Five people have died after a man killed his children in a California church before turning the gun on himself on Monday, according to reports.

The gunman fatally shot the group, including three children under the age of 15, inside the church in Sacramento around 5 p.m., according to law enforcement.

The fourth victim allegedly chaperoned the children, but that person’s relationship to the shooter was unclear early Tuesday.

A police source told NBC News that the shooter used an AR-15-style semi-automatic rifle in the tragic attack.

“We have discovered that there is now a grown man, a father who shot and killed his three children under the age of 15,” said Sgt. Rod Grassmann with the Sacramento County Sheriff’s Office.

“It wasn’t a random shooting,” Grassman said, adding that the shooter and the victims “all knew each other.”

Grassman also said the shooter had a restraining order filed against him.

“As far as I can see, at this point, this is a domestic violence type of incident,” he said.

A church worker heard gunshots around 5:07 p.m. and called the police.

California Governor Gavin Newsom addressed the violence on Monday and mourned the loss of the children.

“Another senseless act of gun violence in America – this time in our backyard,” Newsom tweeted. “In a church with children inside. Absolutely devastating. Our hearts go out to the victims, their families and their communities. »

A witness reported seeing a victim being removed from the church, according to the report.

A massive police presence could be seen near the location on Monday evening as the scene remained active.

“Please be aware and on the lookout. Local law enforcement is responding to a mass county shooting at a church at 2041 Wyda Way,” Sacramento City Councilman Eric Guerra tweeted. Please be vigilant when in the area as local law enforcement responds.”