At least five people, including three children, were killed after a man opened fire in a church near Arden Fair mall in Sacramento, the capital city of California.
The gunman, who killed himself later, was the father of the three children. The bloodshed, which occurred at around 5.00 p.m. local time on Monday, stemmed from a domestic violence incident, Xinhua news agency reported citing the local media.
Sgt. Rodney Grassmann, spokesman for the Sacramento County Sheriff's Office, was quoted by the Sacramento Bee newspaper as saying that the three children killed were all under 15 years.
The fourth victim shot dead on the scene was an adult. Grassmann said the victim's connection to the gunman wasn't immediately clear, adding that victims "all knew each other".
Sacramento City Councilman Eric Guerra referred to the incident as a "mass casualty shooting" at a church in a message, urging people to be alert in the area.
Weighing in on Twitter just after the shooting, California Governor Gavin Newsom said: "Another senseless act of gun violence in America -- this time in our backyard. In a church with kids inside. Absolutely devastating."