Police say four children returning home from school found their mother dead in the kitchen, and then paramedics found the father dead in what police are calling a murder suicide.

The killings occurred three weeks before the father was to be sentenced in a larceny case.

"There was definitely some problems" in the marriage, Detective Sgt. Greg Leismeister said at a news conference at Nassau County Police Headquarters.

He said police went to the North Bellmore home of Thomas and Sherrelle Hayes at about 3:30 p.m. Tuesday after the Hayes' 13-year-old daughter called 911.

Leismeister said the girl had arrived home at about 3 p.m. and was told by her father through a locked front door to pick up her three younger siblings at school. When all four arrived a half hour later, they found the front door still locked. One of the children entered through a back door and let the others inside.

"All four children, unfortunately, found the mother," Leismeister said. The other children were only described by police as a 10-year-old girl and 9- and 7-year-old boys.

Sherrelle Hayes, 43, was lying on a floor inside a laundry room, he said. Police theorize she may have been fatally stabbed several hours earlier in the kitchen and that Thomas Hayes, 44, later moved the body to the laundry room.

The children fled the house, and called 911. When police arrived, they found Thomas Hayes hanging in an upstairs bedroom. Paramedics attempted CPR, but he was declared dead at a hospital.

Thomas Hayes worked as a fire safety inspector in Manhattan. He was arrested on federal larceny charges and pleaded guilty earlier this year, admitting he took discarded prison uniforms, old telephone equipment and other items from a federal building in lower Manhattan and sold the items on eBay for about $25,000, said defense attorney Marc Gann.

Hayes was scheduled to be sentenced May 22, but Gann said he expected his client would likely receive probation or home detention.

Gann said there was no indication that Hayes was depressed over the court case.

"I was flabbergasted when I heard," Gann said. "He was a hard-working quiet, respectful guy who seemed to be a good family man. I am shocked that anything happened of this nature."

Leismeister said police uncovered evidence of marital discord between the couple, but did not elaborate. Police had no records of ever being called to the home for any domestic violence calls or other issues.

Neighbor Michael Sudlow told reporters he had known the couple for more than 10 years and his daughter attended elementary school with one of the Hayes children.

"When I heard what happened I was in shock," he said. "They were always the nicest couple. If you were looking for your kids they would always be over their house playing. They always helped run the local block party here."

Another Bellmore woman who attended the block parties was equally stunned.

"When they do something like this who is going to suffer are the children," said Laura Rocha. "All these children are going to deal with no mother or father. If he snapped he could have gotten help. Now these four children have no parents."

Get the latest from NBC 4 New York anytime, anywhere. Follow us on Twitter, Facebook and Google+. Get our apps here and sign up for email newsletters here. Get breaking news delivered right to your phone -- just text NYBREAKING to 639710. For more info, text HELP. To end, text STOP. Message and data rates may apply.