A sheriff’s deputy was fatally shot in his patrol car in Palmdale, Calif., on Saturday, the Los Angeles County Sheriff’s Department said.

A passer-by found the deputy, Ryan Clinkunbroomer, unconscious near Palmdale Sheriff’s Station around 6 p.m. He was rushed to a hospital, where he died from his injuries.

Sheriff Robert Luna said at a news conference that the police were investigating the episode and urged witnesses with information to contact homicide investigators or leave an anonymous tip. He added that investigators believed that the killing was captured on surveillance video and were analyzing a video that had been circulating online to determine whether it was related.

Officer Clinkunbroomer, 30, had worked in the sheriff’s department for about eight years, Sheriff Luna said, following in the footsteps of his grandfather and father. For the past year and a half, he also trained and supervised deputies. “Not just anybody becomes a field training officer,” he said. “It’s usually the best of the best.”

Officer Clinkunbroomer had gotten engaged just four days earlier, Sheriff Luna added.

Janice Hahn, the chairwoman of the Los Angeles County Board of Supervisors, called the killing “senseless and horrific” in a post on social media.

This is a developing story. Check back for updates.