Four people have been killed in a mass shooting at a Halloween party in Orinda, California, according to local reports. Contra Costa County Sheriff's Office confirmed early Friday that it was responding to a “multiple shooting” in Orinda, located just east of Berkeley. KTVU reported that at least four have been killed and several others were wounded. The property was reportedly being rented out on Airbnb for a private party. Witnesses told NBC Bay Area that attendees at the party included Laney College students. None of the witness details have been confirmed by police.