At least four people, including three children, have been killed in a mass shooting at a family gathering in California, authorities say.

The victims were eight, nine, 14, and 21 years old, a spokesperson for the San Joaquin County Sheriff's Office said on Sunday. Eleven others were injured in the incident at a restaurant in the northern city of Stockton.

A suspect is still on the loose and police say they believe the shooting may have been targeted.

The city's deputy mayor earlier stated that the shooting occurred at a children's birthday party. However, police have not confirmed the type of event at which the shooting occurred, except that it was a family gathering.

[A] birthday party should never be a place where families fear for their lives, Deputy Mayor Jason Lee wrote on social media.

The San Joaquin County Sheriff's Office stated the shooting happened shortly before 6 PM local time (02:00 GMT on Sunday), and is appealing to anyone with information, video footage, or who may have witnessed any part of the incident to come forward.

Spokeswoman Heather Brent described the incident as unfathomable, adding: This is a very active and ongoing investigation, and information remains limited.

Early indications suggest this may be a targeted incident, and investigators are exploring all possibilities.

Stockton's Mayor Christina Fugazi called the shooting unacceptable.

Families should be together instead of at the hospital, standing next to their loved one, praying that they survive.

California has some of the strictest firearm laws in the US, and in recent years has faced challenges to them.

In 2021, a federal judge overturned the state's ban on assault weapons, such as the AR-15 rifle. The following year, the US Supreme Court expanded gun rights as it struck down a New York law restricting gun-carrying rights, jeopardizing similar regulation in California.