A father fatally shot his three daughters and a chaperone during a supervised visit at a California church before killing himself, authorities said.

David Mora Rojas, 39, started shooting inside the sanctuary of The Church in Sacramento during a visit just before 5 p.m. Monday.

Rojas, who was estranged from his daughters’ mother, gunned down the young girls, Samarah Mora Gutierrez, 9; Samantha Mora Gutierrez, 10; Samia Mora Gutierrez, 13; and their chaperone, Nathaniel Kong, 59, according to the Sacramento County Sheriff’s Office. The deranged gunman used an AR-15-style semiautomatic rifle in the attack, law enforcement sources told NBC News.

“[It’s] obviously [beyond] anyone’s rational comprehension,” Sheriff Scott Jones told reporters at a news conference late Monday. “You just don’t know what people are capable of.”

It’s unclear whether Rojas and his children were members of the church or had been using the sanctuary as a neutral meeting site. A spokesman for the Sacramento County Sheriff’s Office told the Los Angeles Times the visit was likely a court-ordered visitation.

The mother of the three girls, who had a restraining order against the gunman, was not in Sacramento during the shooting, but was notified of the deaths by a law enforcement chaplain, Jones said.

“The mom — I don’t know how you process it,” Jones said.

Cops responded to the gruesome scene after a church employee heard gunshots and called 911 after fleeing the building, authorities said.

“I could see that it has an effect on some of them,” spokesman Sgt. Rodney Grassmann told the Los Angeles Times of the responding cops. “You could not go into a scene like that and not be affected.”

The Episcopal Diocese of Northern California denounced the “heinous crime” in a statement Monday, saying the church was a place of refuge for parishioners.

“I am filled with sorrow at this tragedy, compassion for the family left behind, and frustration at senseless violence involving guns,” Bishop Megan Traquair said. “God’s faithfulness and love are greater than our hardest sorrow, and he weeps with us.”

The slayings are being investigated as a domestic violence incident, sheriff’s officials said. Rojas did not have a criminal history in Sacramento, a law enforcement source told the Sacramento Bee.

A woman who lives near the church said she was shocked to learn of the slayings.

“This isn’t the answer,” Sandi Davis, who heard five or six shots as she walked her dog, told the newspaper. “This guy killed his kids. This hurts so bad. Children are innocent, they didn’t have a chance at life.”

California Gov. Gavin Newsom also denounced the shootings as his office coordinated with local law enforcement officials.

“Another senseless act of gun violence in America — this time in our backyard,” Newsom tweeted Monday. “Absolutely devastating. Our hearts go out to the victims, their families and their communities.”

With Post wires