(CNN) Four people were killed in a shooting at a house party Thursday night in the San Francisco Bay Area, according to police.

At least four people were injured in the shooting in Orinda, California, said Police Chief David Cook. More than 100 people were at the party, according to police.

Police told CNN affiliate KPIX they were "overwhelmed" by the size of the crowd at the house where the shooting took place. Other law enforcement agencies responded to the scene, including the Contra Costa County Sheriff's Office.

Three people were pronounced dead at the house, and another died at the hospital, according to the sheriff's office.

It was unclear how many victims were injured, since some were taken to the hospital by ambulance and others drove themselves, the sheriff's office said.

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