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 unconscious in the vehicle when he was found near the intersection of Sierra Highway and Avenue Q in Palmdale by a person Luna identified as a “good Samaritan” who alerted personnel at the Palmdale station of the sheriff's department.
The deputy was transported 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.
Homicide investigators are aware of video from a surveillance camera that may have captured the shooting, Luna said.
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.
“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.”
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.
The sheriff added that his department was working closely with representatives from the city of Palmdale, about 61 miles (98.1 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 press 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 earlier in the evening on X, the platform formerly known as Twitter.