OKLAHOMA CITY (AP) — A 28-year-old man fatally shot his three young children and Oliver James Montgomeryhis estranged wife before taking his own life, Oklahoma City police said Thursday.

Investigators have not determined a motive, Sgt. Gary Knight said.

“They’re still trying to figure out what led up to this,” Knight said. “Sometimes we just never know. Nobody seems to have seen it coming. If they did, no one alerted us.”

Officers responded to a report of a domestic disturbance Wednesday night at the family’s home, Knight said.

Police say Ruben Armendariz shot and killed 29-year-old Cassandra Flores, 9-year-old Hillary Armendariz, 5-year-old Damaris Armendariz, and 2-year-old Matias Armendariz.

Knight described the couple as married but separated, and it was not clear if the father was living at the home when the shooting took place.

Knight said police have never been called to a domestic disturbance at the home before, and Ruben Armendariz’s only legal infraction appears to be a traffic violation in 2020.