Records shed light on Boise man suspected of killing Ada County sheriff’s deputy

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It’s been nearly two months since Ada County Sheriff’s Deputy Tobin Bolter was fatally shot following a traffic stop on the Boise Bench, and despite attempts by law enforcement, there’s still no clear public understanding of what motivated the killing.

Documents obtained by the Idaho Statesman showed 65-year-old Dennis Mulqueen, the Boise man suspected of killing Bolter, as a largely nonviolent person who long struggled with an alcohol use disorder and had numerous — but minor — interactions with law enforcement. Court records reviewed by the Statesman showed Mulqueen’s charges dated back to 2007, ranging from open container violations to failing to appear for hearings.

Police have said Bolter was shot and killed by Mulqueen during an April traffic stop on the Boise Bench. Mulqueen was later shot and killed during a confrontation with police.

“I am not proud of my record, but never considered myself truly criminal and have tried to retain some amount of integrity in life,” Mulqueen wrote to a judge in a 2018 letter asking to reduce a theft conviction from the year before. The Statesman obtained the letter through court filings.

Mulqueen said in the letter that he decided to seek treatment by completing a six-month substance use treatment program at Easterseals-Goodwill Behavioral Health in Caldwell. He said he’d been living in recovery for over a year and a half, and struggled to find full-time employment and long-term housing because of his criminal background. The year before, in 2017, he had been convicted of misdemeanor theft by acquiring lost property when police found him with a lost cellphone.

Mulqueen in the years prior had struggled with homelessness. Paired with his drinking, he said in the letter, that led him to “numerous conflicts with law enforcement.”

Boise police arrest Mulqueen for DUI

Last year, Mulqueen was arrested again for misdemeanor driving under the influence. He was stopped by a Boise officer just after 10 p.m. Sept. 12, 2023, after he drove through a stop sign at the intersection of West Kootenai and South Owyhee streets and was swerving in the lane, according to a Boise police report provided to the Statesman through the public records process.

Mulqueen was arrested and later booked into the Ada County Jail on several misdemeanor charges after he failed a field sobriety test. Boise Police Officer Garrett Britton in the report said Mulqueen became “increasingly agitated” during the arrest and was “lashing out verbally.”

Later testing showed Mulqueen’s blood alcohol content was at nearly 0.14, well over the legal limit of 0.08, according to an Idaho State Police report provided by Boise police.

The Ada County Sheriff’s Office denied the Statesman’s request for investigative reports regarding Mulqueen, citing an exemption under Idaho’s Public Records Act for ongoing investigations.

Mulqueen’s bail was set at $1,500, and he was released from jail after posting the bond at the end of the month, court records showed. Mulqueen was in and out of jail in the following months after he missed hearings and didn’t check in with the Ada County Sheriff’s Office for alcohol and drug testing as part of the terms of his release.

In December 2023, a second warrant with a $3,000 bond attached to it had been issued for Mulqueen’s arrest after he missed another hearing. He wouldn’t be located again until April, when Bolter attempted to conduct a traffic stop roughly two miles from the initial DUI arrest.

Shooting still under investigation, Sheriff’s Office says

Shortly before 9 p.m. April 20, Bolter, who worked the night patrol shift, pulled over Mulqueen’s vehicle near Overland Road and South Raymond Street on the Boise Bench. Before Bolter could approach the driver’s-side window of Mulqueen’s vehicle, he was shot in the neck, according to the Ada County Sheriff’s Office and Ada County Coroner’s Office.

It’s unclear why Bolter pulled over Mulqueen, but he had notified dispatch of the misdemeanor warrant. Body-camera footage for the shooting hasn’t been released, and the Sheriff’s Office denied a request to obtain the footage and investigative reports by the Statesman, citing the ongoing investigation.

Bolter was transported to Saint Alphonsus Regional Medical Center in Boise after three bystanders called 911 and attempted to stop the bleeding. He died at the hospital roughly 12 hours later.

Mulqueen fled the scene and was found later that night outside a home on South Jackson Street by Boise officers. Boise Police Chief Ron Winegar said they attempted for “quite some time” to apprehend him peacefully, but he fired a gun at officers, prompting Boise Police Officer Joshua Sontag to fire back and shoot Mulqueen.

Mulqueen died hours later from a gunshot wound to the chest, the Coroner’s Office said in a news release.

The Ada County Sheriff’s Office said last week that the investigation was still ongoing and that the agency didn’t have any new information.

Law enforcement investigators are still asking anyone who might have had any interactions with Mulqueen in the days before the shooting or any other information to contact Ada County Dispatch at 208-377-6790.

“We’re angry, and we’re confused, and we’re sad,” Ada County Sheriff Matt Clifford said at a vigil in Star, “but the showing of support from the public has given us so much hope.”