A person of interest has been detained in the murder of a Los Angeles County sheriff's deputy shot in his cruiser at a traffic light, authorities said Monday.

Law enforcement technician Kimberly Herrera, with the sheriff's information bureau, said details of the arrest would be released at a briefing later Monday. Earlier, authorities said Sheriff's Deputy Ryan Clinkunbroomer was killed Saturday at about 6 p.m. Authorities had been focusing on a dark gray Toyota that rolled up next to Clinkunbroomer's patrol car moments before his death.

Los Angeles County Sheriff Robert Luna called the shooting a "targeted attack" but said no motive had been determined. He urged people living in the area to check their own cameras for possible clues. And he pledged that law enforcement would "use all of our resources to bring the suspects responsible" to justice.

"He laid everything on the line to serve us," Luna said in a social media post. "He was senselessly murdered."

The shooting took place in Palmdale, a city of 160,000 about 50 miles north of downtown Los Angeles. Luna said authorities were searching for the “vehicle of interest” − the Toyota manufactured between 2006 and 2012.

“Whoever did this, I’d give in,” Luna said Sunday evening. “We are going to find you.”

Developments:

∎ A $250,000 reward is being offered for information leading to the capture of anyone responsible in the slaying.

∎ Gov. Gavin Newsom ordered flags at the Capitol flown at half staff, and a makeshift memorial of flowers and other items grew quickly near the sight of the shooting.

$250K reward offered:Investigators search for assailant who fatally shot Los Angeles County sheriff’s deputy

Details on shooting emerge

Preliminary details indicate that Clinkunbroomer was in uniform and on duty at about 6 p.m. when he stopped his police cruiser at a red light and was shot. The department released grainy surveillance video of a dark-colored sedan that pulled up next to the patrol car, then sped off. A passerby found Clinkunbroomer unconscious in his vehicle a short time later, and fellow deputies raced him to a nearby hospital where he died.

“Without warning, he was murdered while serving our community,” Luna said at a briefing Sunday. “Please, I beg you. Somebody has information. Make things right.”

Who was Ryan Clinkunbroomer?

Clinkunbroomer, 30, was a third generation member of the department, following in the footsteps of his father and grandfather. He was an eight-year veteran of the force who had worked out of Palmdale for the last five years. About 18 months ago he became a training officer, Luna said. Clinkunbroomer had proposed to his fiancée days before the shooting, Luna said.

“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. “Deputy Clinkunbroomer’s devotion to community and country will never be forgotten.”