A lawyer of film director Peter Rodger says the family called police several weeks ago after being alarmed by YouTube videos posted by his son "regarding suicide and the killing of people".
The attorney said police had conducted an investigation and interviewed the man. Police said the man appeared to have trouble making friends but did not find a history of guns.
Police have not formally named the suspect, who died following the attack.
More top news
Twelve people have been killed and three injured after a pick-up truck and a church minibus crashed head-on in Texas.
Revenge porn offenders who attempt to magnify their targets' humiliation will face the toughest penalties under new sentencing proposals.
A remarkably mild night with misty low cloud on the hills of Scotland, Wales and north-west England and further rain in places.