Manhunt underway for sniper who shot Los Angeles sheriff's deputy

A manhunt in Los Angeles county intensified Thursday after a sniper opened fire on a sheriff's deputy.

The deputy, 21-year-old Angel Reinosa, was shot in his bulletproof vest in the parking lot of the Los Angeles County Sheriff's Lancaster station Wednesday by someone in the apartment building across the street, which is a government-subsidized facility.

Lancaster is about an hour north of downtown Los Angeles.

Lancaster Mayor R. Rex Parris said "the only reason that deputy is alive is because he had his vest on."

"He was getting ready to take that vest off," Parris said at a news conference. "Had he done so, it would've been a much more tragic situation."

Sheriff's deputies cleared the apartment building overnight but were not able to identify a suspect.

It is unclear if the person who carried this out lived in the building.

Reinosa has been treated and released from the hospital, authorities said.

He's been with the sheriff's office for about a year and at the Lancaster station for just three months, authorities said.

Sheriff's Sgt. Benjamin Grubb called the shooting a "contemptible assault."

A mental health facility, Mental Health America of Los Angeles, shares a parking lot with the apartment building where the sniper fired from.

A spokesperson for the facility told ABC Los Angeles station KABC that the mental health facility is in the same complex, but separate from the apartments, which are not specifically for patients.

"They let people live in our apartment complex who have mental illness," Terrisa McGhee, who lives in the apartment complex, told KABC. "It's kind of scary because there's no security onsite 24 hours. Management is never here when things happen. The cops are in there constantly. So it's not a surprise."

"It's not just a four-story apartment building, it's a four-story apartment building that is government subsidized for mentally ill people," the mayor said. "I mean, let's call it what it is. Why do you put mentally ill people in a four-story apartment building across from the sheriff's department?"

It is unknown whether the suspect is a patient.

ABC News' Emily Shapiro, Timmy Truong and Marilyn Heck contributed to this report.