In this aerial image made from video shows the scene where emergency workers have cordoned off an area to deal with victims of a shooting, early Wednesday, Oct. 30, 2019, in Long Beach, Ca. (KABC via AP)

LONG BEACH, Calif. (AP) — A gunman who opened fire from an alley into a party killed three people and wounded nine others in California before fleeing in a vehicle, police said Wednesday.

A search was underway for at least one suspect, possibly more, after the Tuesday night attack at a Long Beach home.

Police Chief Robert Luna called the shooter a coward and urged residents to come forward with any information that might lead to an arrest.

"We need to get these dangerous people off the street," he said.

Authorities believe the shooting was planned, though a motive had not yet been determined and there was no evidence it was gang-related.

"I don't believe this was just a random act of violence," Luna said.

Police said a man with his face concealed fired the shots from an alley behind the home into the gathering of 25 to 30 people, including a group of co-workers, then fled in a vehicle.

Luna said arriving officers found a horrific, bloody scene.

Three men were killed, and seven women and two men were taken to hospitals with gunshot wounds. Their conditions could not be immediately determined.

The names of those killed have been withheld pending family notification.

Luna said he doesn't remember a case with so many victims in the coastal city of 470,000 people after more than three decades working there.

In this aerial image made from video shows the scene where emergency workers have cordoned off an area to deal with victims of a shooting, early Wednesday, Oct. 30, 2019, in Long Beach, Ca. (KABC via AP)
Police investigate the scene of a shooting on the E. 7th Street in Long Beach on Wednesday, Oct. 30, 2019. The shooting happened in a backyard of a home behind a nail salon. (Scott Varley/The Orange County Register via AP)
Police close off the scene of a shooting  on E. 7th Street in Long Beach on Wednesday, Oct. 30, 2019. The shooting happened in a backyard of a home behind a nail salon. (Scott Varley/The Orange County Register via AP)
Police investigate the scene of a shooting in Long Beach on Wednesday, Oct. 30, 2019. The shooting happened in a backyard of a home behind a nail salon. (Scott Varley/The Orange County Register via AP)
Police close off the scene of a shooting in Long Beach on Wednesday, Oct. 30, 2019. Authorities say three people were fatally shot and nine others injured at a home in Long Beach, California.(Scott Varley/The Orange County Register via AP)
Police gather outside a mobile command post as they investigate the scene of a shooting in Long Beach on Wednesday, Oct. 30, 2019. Authorities say three people were fatally shot and nine others injured at a home in Long Beach, California.(Scott Varley/The Orange County Register via AP)/The Orange County Register via AP)
Long Beach Police PIO Jennifer De Prez gives information at the scene of a shooting in Long Beach on Wednesday, Oct. 30, 2019. Authorities say three people were fatally shot and nine others injured at a home in Long Beach, California.(Scott Varley/The Orange County Register via AP)