Eight people ages 16-24 were struck by gunfire outside a house party in Carson, California, early Saturday, authorities said.
The worst of the injured were two people in critical condition at medical facilities, said Los Angeles Sheriff's Department South Patrol division chief Myron R. Johnson.
Six others were said by sheriff's officials to have been critically injured but now are likely to recover; one has been released from a hospital.
Ages and genders for the victims were unavailable, according to the L.A. County Sheriff's Department. Los Angeles officials spoke at an afternoon news conference in Carson on Saturday.
"Everyone is expected to recover," said Lt. Rick Conte of the L.A. sheriff's gang-focused Operation Safe Streets Bureau.
In the first minutes of Saturday, sheriff's deputies, who serve Carson under contract, rushed to a residential neighborhood just a few blocks south of the city's well-known Ikea retail location. They were summoned after dispatchers handled multiple calls about people felled by gunfire at a Carson home.
Deputies quickly found five gunshot victims in the street and public areas outside a house party, he said. They called for paramedics and rendered first-aid, the chief said.
He said deputies "swiftly arrived," adding that their quick thinking and application of first-aid training "undoubtedly played a major role in minimizing the impact of this tragic event."
Two additional gunshot victims were taken by private vehicle to medical facilities and had non-life-threatening injuries, officials said. A final victim with upper-body gunshot wounds was discovered when the vehicle he was driving hit a brick wall minutes after the gunfire, not more than a quarter mile away from the violence, Johnson said.
Two uninjured people were in that vehicle, he said. The driver, described only as a 16-year-old boy, was hospitalized and is likely to recover, the chief said.
Conte said no gang motivation had been discovered so far, but it was a possibility investigators were pursuing.
Additionally, Johnson said earlier, deputies were probing the possibility a fist fight preceded the mass shooting.
Sheriff's officials at the news conference said it appeared that more than one handgun was recovered from the scene.
The search for the shooter or shooters remained a priority in the county and in the state, officials said.
At the news conference, Carson Mayor Mayor Lula Davis-Holmes said, "We are all devastated by this senseless crime that occurred in our city last night."