Ian David Long, 28, killed 12 people, including a sheriff's deputy, when he walked into a Southern California bar and grill and started shooting Wednesday night, police said.
The recently-identified gunman was also killed, Ventura County Sheriff Geoff Dean told a news conference Thursday, though it was not immediately clear by whom.
An unknown number of people were also wounded during the attack at the Borderline Bar and Grill, a Country & Western venue in the Los Angeles suburb of Thousand Oaks where a crowd had gathered for a night of dancing, drinking, and eating.
"It's a horrific scene in there," Dean said. "There is blood everywhere and the suspect is part of that."
The sheriff's deputy who was killed was identified as Sgt. Ron Helus, a 29-year-veteran of the department, Dean said.
No other victims have been identified. The sheriff said the gunman has not been identified and there was no known motive for the shooting.
“We just dropped to the ground, we heard a lot of screaming. My friend is the DJ so she cut off the music. We just heard a lot of mayhem,” an unidentified man told local reporters
“I was on the dance floor and I heard the gunshots, so I looked back and then all of a sudden everyone screamed 'get down!' Another witness, Teylor Whittler, said.
"It was a huge panic, everyone got up, I was trampled. I was kind of left on the floor until some guy came behind me and grabbed me and dragged me out," he added.
Pepperdine University has stated that students from the university were present during the shooting but does not have further information.
One group was celebrating a friend's 21st birthday party, a witness said.
Matt Wennerstrom, 20, said he first saw a figure with a handgun opening fire on employees at the front desk.
"At that point, I grabbed as many people around me as I could and pulled them down underneath the pool table that we were closest to until he ran out of bullets for that magazine and had to reload."
At that point, Wennerstrom told reporters, he and others threw bar stools to break the windows and shuffle people out of the building
He described the gunman as just over six-feet tall in all-dark clothing.
Accounts about the incident varied widely throughout the early morning hours with initial reports saying the suspect was in custody. But Sheriff Dean has since said that the gunman died at the scene.
Some social media accounts said a bearded man wearing a dark trenchcoat walked in and started shooting.
Witnesses told CNN that patrons were there for the "College Country" night with line-dancing, music, drinks, and food and the place was packed with a young crowd.
When the shots started, some people smashed windows with chairs to escape, witnesses told CNN.
Other witnesses and people posting on social media said that the man might have fired up to 30 times. Others reported fewer shots, and he might have tossed smoke bombs.
Officials said that shots were still being fired when the first officers arrived at the scene.