LONG BEACH, Calif. — Three people were killed and nine were hurt Tuesday night in a shooting at a home in Long Beach, Calif.

The Long Beach Fire Department said officials were called to the home around 10:44 p.m. and came across what authorities described as a mass casualty incident.

Long Beach fire spokesman Jake Heflin said firefighters arrived to “a scene obviously filled with chaos. There were 12 patients involved in this incident.”

The department said three men were dead and nine others were hurt, though their conditions were not immediately available. Most of the dead and injured were in their mid- 20s, police and fire officials said.

Officers found victims inside and outside the home, said Long Beach police spokeswoman Jennifer De Prez. It is unknown if the gunman or gunmen fled on foot or in a vehicle, De Prez said.

It is also unclear how many people were in the home at the time of the shooting. De Prez said some victims may have driven themselves to hospitals.

Few other details were immediately available.

The shooting occurred at a duplex behind a nail salon on 7th Street near Temple Avenue. Some witnesses said there might have been a Halloween party going on at the house when the shots rang out.

Richard Villalobos, 41, who doesn’t live far from the shooting, said he heard numerous gunshots and, less than 10 minutes later, police sirens.

Some residents said they heard up to 20 shots. Oswaldo Morales, 47, said he was in the area when he heard what sounded like several rounds of gunfire — as many as 17 shots.

Then “silence, you didn’t hear a thing,” he said.

Morales said minutes later he heard fire and police vehicles passing through.