At least 12 people have been killed, including a police officer, at a bar in Thousand Oaks, California.
The shooting began at 23:20 local time on Wednesday about 40 miles North-West of Los Angeles.
At least 200 people were reportedly inside the Borderline Bar and Grill at the time of the attack.
Officials say the suspect was found dead inside and have not identified him. They do not yet know his motive for the shooting.
The bar was hosting a college country music night on Wednesday, according to its website.
Footage broadcast on local media showed people being carried away from the scene, apparently with bullet wounds.
Witnesses who were at the bar are describing a scene of panic inside, and say people reportedly used chairs to break windows to escape.
Reports say the suspect, who is described as wearing dark clothing, may have used smoke grenades as well as a gun in the attack.