A gunman killed his three children, their chaperone and himself during a court-supervised visit Monday evening at a church just outside Sacramento, California, authorities said.
The gunman's children were 15 and younger, officials said Monday night. Law enforcement sources said the shooter used an AR-15-style semiautomatic rifle.
Sheriff Scott Jones said at an evening news conference that the mother of the three was notified of the tragedy while she was out of town. The adult appointed by a court to supervise the visit was likely to have been someone amenable to both mother and father, he said.
It "is obviously behind anyone’s rational comprehension," Jones said, adding, "You just don’t know what people are capable of."
Authorities described the father as the subject of a restraining order, possibly as part of a "domestic" case. But many details remained subject to investigation, Jones said.
Names of the victims were not available.
Sacramento County Sheriff’s Sgt. Rod Grassmann said earlier that gunfire erupted shortly after 5 p.m. at the church, which was not named.

Sacramento Mayor Pro Tem Eric Guerra posted an address on social media that corresponded to a small, residential-like location called the Church of Sacramento. Jones said the location hosted multiple denominations.
The address also matched the location in dispatcher radio traffic about the shooting. The Church of Sacramento, a Christian denomination, did not immediately respond to a request for comment.
The neighborhood is in the community of Arden Arcade, which abuts the eastern boundary of Sacramento and was developed after World War II.
The sergeant said that the threat was over and that no other suspects appear to have been involved.