LOS ANGELES, United States -- A father shot dead three of his own children Monday before turning the gun on himself in a US church, police said.

A fifth person also died in the shooting in Sacramento, California, though it was not clear if that person was related to what police said was a domestic incident.

"The suspect in this case, who ended up killing himself, had a restraining order out against him by his estranged wife, the mother of the three children victims," Sacramento County Sheriff Scott Jones told NBC Bay Area.

All three children who died were under the age of 15, police said. Local reports said they were three girls aged 9, 10 and 13.

Jones said the children had gone to The Church of Sacramento, in the Arden Arcade area of the city, for a supervised visit with their father.

Local media reported that authorities thought the fifth victim, whose identity was still unknown, was the person overseeing the visit.

"At 5:07 this afternoon, we received a call that there was a shooting inside the church," Sergeant Rod Grassmann of Sacramento County Sheriff's Office told reporters.

"This is as far as I can see, at this point, a domestic violence-related sort of incident," he said.

Police said they were not looking for anyone else involved in the shooting.

California Governor Gavin Newsom called the murders "senseless" in a Twitter posting.

"Another senseless act of gun violence in America –- this time in our backyard. In a church with kids inside," he said.

"Absolutely devastating. Our hearts go out to the victims, their families and their communities."

Mass killings involving firearms are a distressingly common occurrence in the United States.

Lax gun laws and an insistence on the right to bear arms have repeatedly stymied attempts to clamp down on the number of weapons in circulation, despite greater controls being favored by the majority of Americans.