MARTINEZ  (AP) — The suspect accused of fatally shooting a California Highway Patrol officer during a traffic stop on a San Francisco Bay area freeway had been treated for mental health problems, his father said.

Doctors diagnosed Christopher Boone Lacy as bipolar and put him on lithium during a hospital stay after he suffered a psychotic break while attending San Francisco State University, Lacy's father told KGO-TV.

"He was, like, hallucinating and, and he was very paranoid," Craig Lacy told the station Wednesday.

He said he and his wife noticed that their son began having mental issues when he was growing up in Oregon. Christopher Lacy eventually graduated with a master's degree in computer science from S.F. State before moving to a duplex in Sausalito.

Lacy, 36, shot CHP officer Kenyon Youngstrom without warning Tuesday on Interstate 680 near Alamo. Moments later, another CHP officer shot and killed Lacy at the scene.

Youngstrom was shot in the neck and had his spinal cord severed. The 37-year-old was pronounced dead Wednesday at a local hospital after being taken off life support.

Flags were lowered across the state in honor of the fallen officer as investigators searched Thursday for a motive. Lacy had a drunken driving arrest in Marin County in 2006, but no criminal record beyond that.

Lacy was pulled over for driving with an obstructed license plate. Video from a CHP dashboard camera showed Youngstrom briefly speaking with him when Lacy pulled out a gun and opened fire.

Investigators found a loaded semi-automatic handgun, two loaded ammunition magazines and a knife in the Jeep. Investigators later seized six computers and several hard drives from his home.

Neighbor Howard Braden, 64, described Lacy as smart and easygoing. He said Lacy told him he found programming work that could last up to three months.

"There were no red flags," Braden said. "No one knew he had any guns or weapons."

Craig Lacy said his son had a hunting license and knew how to use a shotgun and a bow. But he said he had never seen him use a handgun.