A YouTube video thought to be linked to the shootings in California sees a young man claiming he will get "retribution" for a lack of interest shown in him by women.
The footage shows a young man complaining that it is "unfair" that he is still a virgin before threatening a mass slaughter of college students and Isla Vista residents.
"It's obviously the work of a madman," the sheriff said of the shooting. "There's going to be a lot more information that will come out that will give a clearer picture of just how disturbed this individual was."
More top news
Tyler the Creator, the US rapper and Odd Future collective co-founder, has been banned from the UK.
Armed police will be on standby at the funeral of a man dubbed 'Mr Big' amid fears that criminal gangs could cause violence.
A man has claimed he robbed a bank to fund cancer treatment for his young daughter who suffers from a rare from of eye cancer.