At least seven people were injured and the suspect also died during the drive-by shooting on Friday in Isla Vista, near the campus of the University of California Santa Barbara. It was unclear whether the fatal shot was self-inflicted or delivered by police.
Peter Rodger, an assistant director of the 2012 Hollywood blockbuster "The Hunger Games," believes the attacker was his 22-year-old son Elliot, lawyer Alan Shifman told reporters, although that was not immediately confirmed by police.
"The problem with an incident like this is it's obviously the work of a madman," Santa Barbara County Sheriff Bill Brown told a news conference yesterday.
"We have obtained and we are currently analysing both written and videotaped evidence that suggests that this atrocity was a premeditated mass murder."
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Authorities said there were nine separate crime scenes in what was a "chaotic" situation.
Shifman, the family attorney, said Elliot Rodger had been diagnosed as being a "highly functional Asperger's Syndrome child" and was being treated by "multiple" professionals.
ABC News also identified the shooter as Elliot Rodger.
Ambulances and police cars swarmed the streets after the shooting -- just the latest in a string of gun massacres that have rocked the United States in recent years.