Russell Smith, a 29-year-old man from Roy, Utah, shot and killed his wife and two young children then turned the gun on himself on Father's Day, missing a family gathering, which prompted relatives that something was wrong, AP reported.

The bodies of his wife, Shawna Smith, 26, and their children, 6-year-old daughter Tylee and 2-year-old son Blake, as well as the gunman's, were found by Shawna's brother when he checked on the family.

The family lives on a quiet, suburban street in Roy, a city of about 38,000 roughly 30 miles north of Salt Lake City.

"She was just an amazing person, and an amazing mother," Sheila Pruitt, Shawna Smith's mother said, reported ABC News. "Those kids were her world."

She added that she knows her son-in-law had hunting weapons but didn't see any signs of violence. Meanwhile, the neighbors also observed that the family looked close and happy.

"Sweetest little family you ever saw. I can't imagine," next-door neighbor LaRue Simpson said Monday. "Something must have gone really wrong yesterday because they were not like that at all."

Neighbor Lynn Everley also noted that they never heard of fights or indications of problems and that they were happy with their jobs.  

Russell Smith was a former employee of the defense contractor L-3 Communications, which said in a statement that it is willing to cooperate with the investigation, the Deseret News reported.

Shawna Smith worked at Busy Bee's Playhouse, a Roy childcare facility, for nearly nine years, director Jennifer Lindstrom said.

Investigators talked to family members and neighbors in hopes of uncovering a motive for the crime.