PALMDALE, Calif. (AP) — A Los Angeles County Sheriff’s Department deputy died after he was shot in his patrol car Saturday evening by an unknown assailant, and an investigation is underway that the sheriff said will press all of the department’s resources into action.

Deputy Ryan Clinkunbroomer, 30, died after being transported to a hospital, Sheriff Robert Luna said during a press conference late Saturday night.

The preliminary investigation showed Clinkunbroomer was driving while on duty and fired upon around 6 p.m., Luna said.

Clinkunbroomer was found unconscious minutes later in the vehicle while waiting for a redlight near the intersection of Sierra Highway and Avenue Q in Palmdale. A person Luna identified as a “good Samaritan” alerted personnel at the Palmdale station of the sheriff’s department.

Police cars block off a street where a sheriff’s deputy was shot while in his patrol car in Palmdale, Calif. on Sunday, Sept. 17, 2023. (AP Photo/Richard Vogel)

The deputy was taken to Antelope Valley Medical Center in Lancaster, where he was treated for a gunshot wound.

“Despite the medical staff’s best efforts to save our deputy’s life, regrettably he succumbed to his injuries,” Luna said.

The sheriff’s department is offering a $100,000 reward for information that will lead officials to an arrest. The City of Palmdale is matching the department’s $100,000 reward.

Homicide investigators are aware of video from a surveillance camera that may have captured the shooting, Luna said. “A vehicle of interest” was seen on camera near the patrol car.

The vehicle of interest is described as a dark grey 2006 to 2012 Toyota Corolla.

“Cowards, that’s what they are,” the Sheriff said in a press conference.

Luna said he believed the shooting was a “targeted attack.” But the motive, and whether the deputy or the department in general was the target, was not yet known.

A local resident waves a Thin Blue Line flag in support of a deputy who was shot while in his patrol car in Palmdale, Calif. on Sunday, Sept. 17, 2023. A sheriff’s department deputy has died after he was shot in his patrol car by an unknown assailant on Saturday, and an investigation is underway. (AP Photo/Richard Vogel)

“We’re going to catch the person who did this,” Luna said. “Because every resource that the Los Angeles County Sheriff’s Department has to bear is going after you.”

“We are not going to leave any stone unturned,” the Sheriff said.

Clinkunbroomer, who transferred to the Palmdale station in July 2018, was a third-generation officer who followed his grandfather and father into the sheriff’s department, Luna said.

California Gov. Gavin Newsom called the killing “horrific, unconscionable, and shocking.” He ordered flags at the state capitol flown at half-staff in honor of Clinkunbroomer.

“In this time of mourning, we honor this legacy and send our deepest sympathies to Deputy Clinkunbroomer’s fiancée, his loved ones, and the men and women of the Los Angeles County Sheriff’s Department,” Newsom said in a statement Sunday. “Deputy Clinkunbroomer’s devotion to community and country will never be forgotten.”

The sheriff said his department was working closely with representatives from the city of Palmdale, about 61 miles (98 kilometers) northeast of Los Angeles.

“Palmdale loves the sheriff’s deputies, and the deputies take very good care of Palmdale and love our community back,” Mayor Laura Bettencourt said at the news conference. “The person that did this is a coward. and they will be caught.”

“It is sickening, heartbreaking news,” Republican state Sen. Scott Wilk, who represents Palmdale, posted Saturday evening on X, the platform formerly known as Twitter.

Clickunbroomer had just gotten engaged four days prior to his murder.