A Kansas man who police said was previously contacted for “aggressive behavior” fatally shot his four young children and their mother before he turned the gun on himself Tuesday, authorities said.

Officers were already at an unrelated car crash two blocks away when they were summoned to a single-family home in Windfield based on a 911 call from a man who identified himself as the shooter, Windfield Police Chief Robbie DeLong said.

“At approximately 8:50 a.m., our officers received a 911 call from a male individual who stated that he had killed his entire family and he was getting ready to kill himself,” DeLong said at a news conference.

The first officer to arrive approached the residence but retreated after hearing a single gunshot, DeLong said. Authorities set up around the home under the assumption they had an armed, barricaded person on their hands, he said.

A little more than two hours after the 911 call, with a regional SWAT team and Cowley County sheriff’s deputies joining the standoff, authorities breached the home and found the bodies, DeLong said.

“I want to make something very clear to the community,” he said. “This was an isolated incident. There is no ongoing threat.”

The dead were identified as the suspect, Ronald H. Williams, 53; mother Kelly L. George, 44; Carol A. Williams, 9; Ronald H. Williams Jr., 7; Sarah K. Williams, 5; and Kelly M. McGee Williams, 3.

DeLong said that police had contact with the father as recently as the last few weeks and that officers have responded to the area of the family’s home in the past based on reports of gunfire but were unsuccessful finding evidence.

“We have calls of just aggressive behavior, but not enough really to act on,” he said.

Williams was a registered sex offender, according to the state sex offender registry. In 1998, a judge accepted guilty pleas by Williams to two felony counts of attempted indecent liberties with a child and one count of battery involving the same victim, a 15-year-old girl, according to Kansas criminal court records.

The Kansas Bureau of Investigation (KBI) has joined the probe into Tuesday’s violence, with a key goal of identifying a motive, DeLong said.

KBI Special Agent in Charge Jason Diaz said agents would seek to interview relatives as well as neighbors.

If you or someone you know is in crisis, call or text 988 or go to 988lifeline.org to reach the 988 Suicide & Crisis Lifeline or visit SpeakingOfSuicide.com/resources.