The gunman who killed three people who work for a California programme that treats veterans for post-traumatic stress disorder was kicked out of the therapy, a relative of one victim said.
Albert Wong, 36, was identified as the man who went to The Pathway House therapy centre on the sprawling campus of the largest veterans home in the country and took a psychologist and two executives hostage, authorities said.
Gunshots were fired around 10:30 am after Wong arrived at the Veterans Home of California-Yountville but nothing more was heard from him or the women until their bodies were found at about 6pm, authorities said.
Wong slipped into a going-away party for two employees of The Pathway Home, authorities said.
Killed were programme executive director Christine Loeber, 48; clinical director Jennifer Golick, 42; and Jennifer Gonzalez, 29, a clinical psychologist with the San Francisco Department of Veterans Affairs Healthcare System.
"These brave women were accomplished professionals who dedicated their careers to serving our nation's veterans, working closely with those in the greatest need of attention after deployments in Iraq and Afghanistan," The Pathway Home said in a statement.
Ms Golick was the top psychologist at The Pathway Home, a non-profit organisation that treats combat veterans of Iraq and Afghanistan.
It was "far too early to say if they were chosen at random" because investigators had not yet determined a motive, California Highway Patrol Assistant Chief Chris Childs said.
However, Ms Golick's father-in-law said she had recently ordered Wong removed from the programme.
Ms Golick called her husband, Mark, at around 10:30 am to say that she had been taken hostage by the former soldier, he said.
Wong had been an Army infantryman who served a year in Afghanistan from 2011 to 2012. He held a number of service awards, including one for expert marksmanship with a rifle.
Yountville, about 53 miles north of San Francisco, is one of the Napa Valley's most upscale towns, located in the heart of wine country.
A sheriff's deputy responding to an emergency call Friday morning got into a shootout with the gunman but was not injured.
Highway Patrol Sgt Robert Nacke said negotiators were unable to make contact with the gunman throughout the day.