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
Charlie Gard's parents have been given until noon on Thursday to reach an agreement with doctors on arrangements for his death.
In a series of tweets, the US president says transgender people will not allowed or accepted to serve their country 'in any capacity'.
The chancellor - having won the argument within Cabinet - has told ITV News he is targeting a swift start to talks on the interim deal.