SCRANTON ? After his wife left for work, Michael L. Shirley killed his three children at their home in this small northeast Kansas town, set fire to the living room, then shot himself, investigators said Wednesday.

Osage County Sheriff Laurie Dunn said Shirley, 52, suffered a shotgun wound in the upper torso but died as a result of the fire. Dunn said other evidence determined the death was a suicide, but would not elaborate.

The sheriff wouldn’t specify how the children died, but she eliminated the fire or gunshot wounds as possibilities.

The Kansas Fire Marshal’s Office ruled the fire was arson shortly after the mother, Amy Shirley, and a neighbor found the bodies Monday morning.

Dunn identified the children as 14-year-old Ethan C. Shirley, 11-year-old Ashten C. Shirley, and 9-year-old Caleb Jackson Shirley. She said there was no evidence the children had been bound or restrained.

She also said investigators still were trying to determine a motive. Dunn also said that Amy Shirley told authorities that everything seemed normal when she left for work.

“There’s a mom who had her whole world turned upside down two days ago,” Dunn said. “There’s nothing to show she was involved.”

Michael and Amy Shirley had been married for about 15 years, Dunn said, adding: “We’re still working on the relationship status.”

Wally Roberts, fire marshal investigator, said some type of accelerant, such as gasoline or diesel fuel, was poured on the living room floor and furniture. He said the fire went out after about 15 minutes.

Dunn said Amy Shirley left for work in Topeka about 6:30 a.m. Monday and later received a call from her children’s school that they weren’t there. After nobody answered the phone at home, she returned to the house with a neighbor. The fire was already out when Amy Shirley arrived, Dunn said, and she called authorities around 10:40 a.m.

Dunn said Shirley is staying with relatives and has refused all media requests for interviews.

The deaths shocked the small town of about 725 residents, about 20 miles south of Topeka. The last homicide in Scranton was in the 1970s.

Dunn said that during her 28 years with the sheriff’s department she has never investigated a homicide case with that many deaths or one in which children were killed.