The gunman who went on a chaotic rampage killing four people before being fatally shot by police at a college campus planned the attack and was capable of firing 1,300 rounds of ammunition, the police chief said.
"Any time someone puts on a vest, of some sort, comes out with a bag full of loaded magazines, has an extra receiver, has a handgun and has a semi-automatic rifle, carjacks folks, goes to a college, kills more people and has to be neutralised at the hands of the police, I would say that that's premeditated," Santa Monica Police Chief Jacqueline Seabrooks said.
CNN reported that the killer was identified as John Zawahri, who would have turned 24 on Saturday.
Investigators were looking at family connections to find a motive because the killer's father Samir Zawahri, 55, and brother Chris Zawahri were the first victims, one source said.
CNN also said the gunman had mental health issues. A few years ago, he was admitted to hospital for treatment after allegedly talking about harming someone, it quoted one official as saying.
Not long after arriving at the neighbourhood, the gunman's father and mother went through a difficult divorce and split custody of their two boys, said Thomas O'Rourke, a neighbour. "It was not an easy break-up," O'Rourke said. "It was a bitter divorce."
Public records show Randa Abdou, 54, the ex-wife of Samir Zawahri, was the former co-owner of the house where the first shooting took place. The mother was out of the country visiting relatives and was not expected home for another week.
The gunman was enrolled at Santa Monica College in 2010, Seabrooks said.
After neighbours watched in shock as he shot at his father's house and it went up in flames, he opened fire on a woman driving by, wounding her, and then carjacked another woman.
He directed her to drive to the college campus, having her stop so he could shoot along the way, police said. He fired on a city bus, injuring three women.
The gunman also fired on police cars, bystanders and pedestrians, police said. From there, the chaos shifted to the college.
In a faculty car park, he fired on two people in a red SUV. The driver was killed and a passenger was in critical condition.