A 3D rendering of a DJI Mavic 2 Pro drone hovering over a 3D-rendered scene that includes a man lying dead in front of an undercover police truck.

Footage of Sean Monterrosa’s killing by police was ‘overwritten.’ Here is what we know about that night.

Footage of Sean Monterrosa’s killing by police was ‘overwritten.’ Here is what we know about that night.

By Laurence Du Sault
and Geoffrey King | December 9, 2021

As Vallejo moves to fire the detective who killed Monterrosa, newly-released records raise questions over officials’ handling of investigation.

Paramedic Billy White dropped his drone lower to the ground as he sought a clear view of the unrest unfolding at the Walgreens in Vallejo, Calif. following the murder of George Floyd. From the screen of his 10-inch iPad, White observed in real-time as people clutching stolen medication bottles slipped through the broken pharmacy window near his work.

Coworkers had crowded around White to watch the video feed when an unmarked police truck sped into the parking lot.

As it came to a stop, White saw the vehicle’s windshield “light up with bullets,” he later told investigators. An officer jumped out of the truck, pointing a rifle.

Then White noticed a body on the ground.

“Oh shit,” a coworker said.

White’s drone recorded the killing of 22-year-old Sean Monterrosa in high definition, records from the homicide investigation show. Within an hour of the shooting, the device was taken to the office of Police Chief Shawny Williams, where it stayed for several hours, bypassing department protocol. When the chief gave the drone to a detective shortly after 4 a.m., the video file had been overwritten with zeros, according to reports by Vallejo police and a forensics expert with the United States Secret Service.

The only known visual record of the shooting was permanently lost.

White told investigators that his drone captured the incident from start to finish. Open Vallejo recreated the position of the drone using police reports, body camera footage in which the drone is visible, and other open source information. White’s Mavic 2 Pro drone has a mechanically-stabilized camera that records 4K video at 60 frames per second. Reconstruction by Josh Davis / Special to Open Vallejo

Now, nearly a year and a half later, Williams has moved to fire Det. Jarrett Tonn after outside investigators hired by the city found that he and three other officers violated department policies in their “reckless approach” that left Monterrosa dead. Vallejo hired the private consulting firm OIR Group to conduct an administrative investigation into whether officers had followed department policies and tactics. California Attorney General Rob Bonta announced in May that his office would conduct a separate criminal review of the shooting, which is ongoing, to determine whether criminal charges are warranted.

Williams declined to comment for this story.

Tonn, who last week received a notice of intent to terminate his employment, is the first officer in Vallejo’s history of 33 known fatal incidents since 2000 to face being fired for using deadly force. He was placed on leave in June after the OIR Group found he used excessive force when he shot Monterrosa from the backseat of the police truck, striking him once in the back of the head. 

The OIR Group also found that Tonn, as well as detectives Bretton Wagoner, Wesley Pittman, and Capt. Lee Horton, violated department policies related to de-escalation, satisfactory work performance, and body camera activation. Horton retired last week after 23 years with the department, days before the report’s release. Wagoner left the department in September to join the Napa County Sheriff’s Office. At the time of publication, Pittman had not been served with a notice of intended discipline, sources told Open Vallejo. All four officers declined to comment for this story.

The OIR report was part of a larger set of documents the city disclosed on Thursday that included police reports, crime scene photographs, interview audio, and other records relating to the Monterrosa investigation. Open Vallejo sued the city in September for these and other police records. The documents shed new light on the series of events that led to Monterrosa’s death and the loss of critical evidence in the case.

‘Extremely rushed, unplanned, and aggressive’

June 2, 2020 had been an “unusual” night, officers would recall in interviews with OIR Group’s Stephen Connolly, former executive director for the Orange County Office of Independent Review, and Michael Gennaco, a former federal prosecutor and the head of the firm. Gennaco and Connolly reviewed investigative materials and re-interviewed the officers involved, aside from Horton, who was on medical leave at the time. The officers had been interviewed by Vallejo investigators in the hours after the shooting.

Reports of looting were pouring into the Vallejo Police Department, and Horton, Pittman, Wagoner, and Tonn had been called in outside their usual work hours, records show. Their task was to enforce a citywide curfew established by the Chief of Police in coordination with city management, according to an interview with Horton connected to the homicide investigation. As for Pittman, he told OIR Group that he thought their job was to safeguard “high value” businesses from looting and “protect the department” if protests erupted. 

At 12:35 a.m., Horton noted via “air priority” radio traffic that he was observing looting at the Walgreens at the corner of Redwood and Broadway Streets, records show. 

The detectives pulled up next to Horton’s patrol SUV seconds later. Wagoner drove the unmarked truck while Pittman sat in the passenger seat, holding a flashbang grenade. Tonn sat in the middle behind them. 

Horton “hurriedly” laid out a plan: he would head north to enter the parking lot from Broadway while the three detectives came in from the south entrance, according to the report. Horton then sped off in an apparent signal to engage, the report found. The entire exchange lasted between 5 and 15 seconds, the detectives told OIR. 

Moments later, Horton gave the detectives a heads-up on the radio. “It looks like they’re armed, possibly armed,” Horton said

At 12:36 a.m., the two vehicles stormed the parking lot, causing people to flee in separate vehicles, leaving only Monterrosa. That is when the young man “abruptly turned toward the officers, crouching down in a half-kneeling position as if in preparation to shoot,” according to a statement the department released the next day.

Tonn positioned his Colt M4 Commando rifle between his colleagues and, without warning, fired five high-velocity rounds at Monterrosa through the windshield, the OIR investigators found. At 12:37 a.m., an officer reported that shots had been fired. 

“What did he point at us?” Tonn asked after exiting the vehicle. “Hey, he pointed a gun at us.”

But Monterrosa had only an iPhone in his hand. Detectives later removed a hammer from the front pocket of his sweatshirt.

Tonn’s “mistaken assumption” that Monterrosa was armed and preparing to shoot was largely predicated on the way in which the officers approached him, the OIR report found. The officers’ tactics left no margin for error and catalyzed Tonn’s “unduly extreme” interpretation of Monterrosa’s actions, which were “potentially consistent with an intent to surrender — a theory reinforced by the reality that he did not in fact have a gun.”

The report found discrepancies between officers’ statements that Monterrosa was “facing them in an aggressive shooting stance at the time Detective Tonn shot him” and autopsy results showing the bullet entered the back of his head.

“What is known is that the fatal round to Mr. Monterrosa struck the back of his head, suggesting that he had turned away from the detectives (and was less of a legitimately perceived threat) when he was fatally struck,” the OIR investigators wrote. And by firing through the windshield, Tonn gave up the possibility to reassess the level of threat in-between shots due to broken glass obstructing his vision, the report continued.

An closeup of an undercover Vallejo police pickup truck with five bullet holes in the windshield, fired from inside the vehicle.
The windshield through which Det. Jarrett Tonn shot Sean Monterrossa is seen in a Vallejo Police Department evidence photograph taken on June 2, 2020 in Vallejo, Calif.

A suspected bullet hole was also identified on the driver’s side door of a vehicle that had fled the scene, the report noted, suggesting that Tonn did not have a safe backdrop when he fired, contrary to statements he made to investigators. Neither the records released by the city of Vallejo nor San Mateo Crime Lab reports obtained by Open Vallejo suggest any forensic analysis was performed on the hole.

The report faulted all four officers for violating de-escalation policies requiring them to consider other feasible force options before lethal force. “The extremely rushed, unplanned, and aggressive nature of the VPD response” was a critical factor in determining whether other alternatives should have been considered, the investigators wrote.

In fact, the report found the altercation likely could have been avoided altogether. 

“Other than preventing a potential burglary in progress, there was no apparent need for immediate control of the subject,” the report read.

Although Horton was their superior and answered only to the chief, the report found that the three detectives “should have pushed back on [the captain’s] rash approach to the burglary activity at the Walgreens.”

The report found the officers violated the department’s satisfactory work policy for the same reasons.

Gennaco declined to comment on the firm’s findings, citing ongoing legal proceedings related to the shooting.

It would have taken Billy White approximately one minute to fly his drone between Medic Ambulance and the Walgreens on Redwood Street in Vallejo, Calif. Noah Berger / Special to Open Vallejo

‘I saw the guy running away’

From a temporary command post outside the local Best Buy, a two-mile drive from the Walgreens, Williams and incident commander Capt. Jason Potts heard the reports of shots fired over the radio, records show. They had been monitoring police activity and coordinating with Horton throughout the night; between 9:00 p.m. and 12:36 a.m., the chief and captain spoke approximately 20 times, Horton later told investigators. But there is no indication that Williams filed a report regarding his involvement that night. The OIR Group, which according to the report was “acting under the authority of the Chief of Police,” did not mention Williams but for a footnote that the chief strengthened the department’s de-escalation policy in 2019.

Potts immediately headed to the scene, where he learned the drone had recorded the shooting. Potts dispatched Ofc. Brad Kim to collect the device from the Medic Ambulance office where White worked, records show

In an exchange captured by Kim’s body camera at Medic Ambulance around 1:20 a.m., White explained what he witnessed.

“I saw the guy running away,” he said. “But then I looked and I was like, oh, he’s down.”

Without further questions, Kim ended the interview, less than four minutes after it began. He picked up a paper grocery bag containing the drone, iPad and controller and headed back to Vallejo police headquarters, where he handed it to Potts at 1:34 a.m. This concluded his involvement in the case, he wrote.

Potts claimed he initially locked the drone in his office, according to a chain of custody report written more than nine weeks after the shooting. But minutes later, he carried the drone to the chief’s office so investigators could use the room to sequester Wagoner, according to the report. The drone remained in the paper grocery bag until it reached Williams’ office, where it was placed in a locked cabinet, Potts wrote.

Neither Kim, Potts, or Williams booked the device into evidence despite a policy that requires that any employee who first collects property retain and book it into the evidence room before going off-duty, after which the evidence is carefully tracked by trained, non-sworn personnel. The policy allows a supervisor to bypass this requirement.

The drone remained in the chief’s office until 4:10 a.m., records show; what unfolded in those more than two hours remains unknown to all but those closest to the chief. When Williams and Potts transferred custody of the drone to Det. Kevin Rose, a former software developer, Rose was unable to open the two video files that correlated to the approximate time of the shooting, records show. In a report detailing the steps he took to recover the footage, Rose wrote that he eventually “formed the opinion that there is some problem with the SD card within the drone on which the videos had been recorded.” 

Five days after the shooting, Rose shipped the drone to the U.S. Secret Service National Computer Forensic Institute in Tulsa, Okla. The Secret Service confirmed on June 25 that the footage of the shooting was gone.

“Specifically, the video taken with the drone on or about 06/02/2020, had the folder structure intact,” wrote Special Agent Stephen Baskerville, “but all of the internal data had been overwritten with ‘0’s’,” rendering the video files unrecoverable. 

“Upon further research into DJI devices,” Baskerville continued, “it was determined that this ‘overwrite’ occurs when the device (drone) is improperly shutdown.”

But in an interview last September, White told Open Vallejo that he and his colleagues handled the evidence appropriately, adding that he believed police could be counted on to do the same. He did not further comment on the shooting, but records show White had asked a coworker to wait by the drone and prevent anyone from touching it or powering it down until police arrived. 

The coworker who safeguarded White’s drone told Rose it was still powered on and connected to the iPad when police arrived at the Medic Ambulance office to seize it. Even after Rose retrieved the device from Williams’ office, downloaded the videos and conducted several attempts to recover the files, the battery remained at 3%, he noted in his report. The next day, Rose called White to ask about a charger and second battery, which a district attorney investigator retrieved and brought to Vallejo.

Rose left Vallejo earlier this year to join the Placer County Sheriff’s Office. He declined to comment for this article.

‘They circle the wagons on everything’

A police officer walks into the Vallejo Police Department at night.
A police officer enters the Vallejo Police Department on Sunday, Nov. 21, 2021, in Vallejo, Calif. Noah Berger / Special to Open Vallejo

Vallejo officers interviewed White on at least four occasions. He told investigators on June 4 that he had not seen in detail what Monterrosa was doing at the time of the shooting, as he was concentrating on radio traffic and controlling the drone. 

On June 8 — White’s third interview — Det. Jason Scott told him that investigators had failed to recover footage of the killing. More than a month later on July 23, Rose called White for a fourth interview, documented in a police report, in which White added several details not reflected in his previous statements. White claimed that he heard someone say “gun, gun, gun” on the radio prior to the shooting. He also said that he saw Monterrosa’s hammer “fly up in the air” as he turned toward the officers, though body camera footage shows detectives located the hammer inside the pocket of his hoodie. 

In that last documented interview, White discussed in greater detail potential corruption of the drone files, according to the OIR report. He alleged for the first time that he had noticed that the video file of the shooting appeared to be zero seconds long instead of the 14 minutes he had anticipated upon returning to Medic Ambulance that night. White also told Rose that video files from his drone had become corrupted in the past.

OIR noted that White made these new observations after it had “become apparent that the drone recording itself was not retrievable.” The report found that his statement about a “gun, gun, gun,” as well as “other specific aspects of his supplemental statements were not corroborated by other evidence.”

During the July 23 interview, White confirmed that both Monterrosa and the undercover police truck were “in the drone’s frame of view at the same time” during the shooting, according to Rose’s summary of the interview.

White said in a second interview with Open Vallejo Tuesday that he remains confident in the department’s post-shooting investigation. Asked to comment on a summary of the drone’s chain of custody which showed it stayed in the chief’s office for hours, White said it would be “outlandish” to believe that Williams deliberately destroyed evidence. 

Footage from Det. Wesley Pittman’s body camera shows Billy White’s Mavic 2 Pro drone hovering within view of Sean Monterrosa’s body and the undercover police truck from which he was shot.

Confusion about the drone persisted for months following the shooting. After the U.S. Secret Service sent the device back to Vallejo police, Rose arranged to have it transferred to the FBI’s Sacramento Field Office, records show. Almost four months after the shooting, Potts responded to an email thread about the investigation on which then-Interim Police Chief Joseph Allio, Williams, Det. Sgt. Mathew Mustard and Lt. Drew Ramsay were copied. 

“Any info on the FBI and UAS?” Potts wrote, abbreviating the technical term “unmanned aerial system.”

“Can you clarify your request about FBI and UAS???” Ramsay responded. 

No one answered his question.

Last summer, with the help of the ACLU, Open Vallejo obtained the corrupted files on the drone’s SD card after the City of Vallejo initially claimed it had no responsive records.

Open Vallejo submitted the files for analysis to David Kovar, a leading digital forensics researcher and one of a small number of practitioners in the field of drone forensics.

“I looked at the files and I came to the same conclusions that you did: that they were unreadable by any normal means,” Kovar said. Given the available information, Kovar said, he could not give a conclusive statement as to the cause of the data loss.

“It’s possible that the SD card, as reported, was malfunctioning,” Kovar said of the theory that the footage was lost to an unavoidable glitch. “It is also possible that somebody prior to that analysis did use some sort of file-wiping tool to zero out files that were potentially damaging” to the department.

Kovar found it unusual that the folder structure of the files remained intact but their contents were zeroed out, noting that he had never seen such data loss happen on its own. And while he gave “a fair bit of credence” to the Secret Service report suggesting the drone could have been improperly shut down, Kovar noted the care White reportedly took to prevent this issue from happening.

There is at least one option that may still yield answers, Kovar said: examine each computer that came into contact with the drone or its memory card on the night of the shooting. And while the passage of time can complicate forensic analysis, he said, the inquiry would benefit from a clearly-defined starting point.

“Any evidence of the SD card in question being accessed or modified would most likely be on the computers in the chief’s office — assuming that no one else had access to the drone during the period in question,” Kovar said. 

The lack of transparency around the drone has fueled speculation that its footage was either deliberately or negligently overwritten. 

Open Vallejo asked five current or former Vallejo officers for their opinions on what happened to the missing footage. Speaking on condition of anonymity because they were not authorized to discuss sensitive law enforcement matters, each of them criticized the handling of evidence in the case, noting that the drone should have been booked into evidence right away. One declined to speculate about how the data became corrupted, but added that without the proper evidence tracking system in place, “there’s no way you can say for sure that nobody in that office touched it. That’s why you have a chain of custody.”

Two others said they believed the drone was deliberately wiped, noting that destruction of evidence, if committed by a police officer, is a felony. One of them said the circumstances seemed reminiscent of the 18½-minute gap that appeared in a key White House tape during the Watergate scandal. 

Another officer said they believe it is more likely the data was inadvertently corrupted during its time in the chief’s office. And a fifth said they did not believe that either Potts or Williams had the technical knowledge to overwrite the data on the card, and that the most likely scenario was that the file corruption occurred prior to human intervention.

At the same time, the officer said of city officials and police command staff, “They circle the wagons on everything.”