A Los Angeles County sheriff's deputy died after he was shot inside his patrol car Saturday evening, authorities said.

Deputy Ryan Clinkunbroomer, 30, was found unconscious by a civilian in his patrol car around 6 p.m. in front of the sheriff's station in Palmdale, according to the Los Angeles County Sheriff's Department. Palmdale is about 60 miles north of Los Angeles.

The deputy, who was uniformed and on duty when he was shot, was pronounced dead at a local hospital, Los Angeles Sheriff Robert Luna said at a news conference.

It's unclear who opened fire on the deputy. The department is asking the public to come forward if they have video that may have captured the shooting.

"We really need your help. We need to get this guy off the street -- guy or guys. He's a public safety threat. He ambushed and killed -- murdered -- one of our deputies. We need your help to get him off the street," Luna said.

Luna said it appears to have been a targeted shooting.

"I think it was a targeted act based on what we know now, but we're still in the extremely early stages of this investigation," Luna said.

"He was just driving down the street and for no apparent reason -- and we're still looking into the specific reasons -- somebody decided to shoot and murder him. ... That to me is sickening. "

Clinkunbroomer was a field training officer, and his father and grandfather both served in the sheriff's department, Luna said. He had just gotten engaged four days ago.

"He was just starting his life," the sheriff said.

Saturday's shooting comes three years after two Los Angeles deputies were shot ambush-style at a train stain while sitting in their patrol vehicle. Surveillance video from the incident showed a gunman walking up to the passenger door of their squad car, opening fire and running away.

This is a developing story and will be updated.