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."
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British soldiers will join troops from some 30 countries who work in the country.
The demand comes after the Prime Minister urged a "grown up" relationship between her government and the devolved administrations.
The rapper failed to make it to London in time as he had problems with his passport.