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
MI5 face mounting pressure over claims the IS executioner 'Jihadi John', named yesterday as a London graduate, was known to them
Labour leader Ed Miliband is due to set out his party's plans on how it would cut tuition fees.
New drug driving laws are to come into effect next week, including laws on some prescribed medications.