At least four people have been killed and 10 more injured at a Halloween party in Orinda, California, overnight, local media reports say.
According to police officials, an investigation is underway.
According to an NBC reporter, the incident happened at a rented Airbnb apartment.
A KTVU reporter quoted a neighbour who said that he heard gunfire coming from the house where one of the apartments had been rented through Airbnb for a party.