Dec. 18 (UPI) — Authorities in Utah investigating the shooting deaths of four family members and a critically injured teen said Wednesday that evidence suggests the father attempted to kill his wife and four children before turning the weapon on himself.

The gruesome scene at a residence in the 3700 block of Oxford Way in West Valley City, a suburb of Salt Lake City, was discovered Tuesday afternoon by a concerned relative who had not heard from the family’s 38-year-old mother for sometime.

The relative had found the 17-year-old son in the garage suffering from a gunshot wound. Police then discovered the 42-year-old father, 38-year-old mother, 11-year-old son and two daughters, ages 9 and two, inside the home.

Circumstances surrounding the mass murder were not initially clear, as authorities had to wait until a search warrant was granted, which occurred Tuesday night, before a thorough investigation could commence.

In an update Wednesday, Roxeanne Vainuku, deputy communications director for West Valley City, told reporters that a handgun believed to have been used in the shooting was found under the body of the father.

“The father likely shot all of the members of the family and then himself,” She said. “However, we do need to wait for confirmation from ballistic evidence and from forensic evidence to be able to determine that definitely.”

The 17-year-old son remains hospitalized in critical condition.

Vainuku would not comment on the specific injuries sustained by the four deceased victims, but said the surviving son was shot in the head and was suffering from a severe brain injury.

“So that, I think, clarifies a lot,” she said.

The mother and two daughters were found dead in an upstairs bedroom, while the father and 11-year-old son were discovered in the living room.

Vainuku said the surviving son was not shot in the garage but had somehow made his way there after being wounded.

Authorities suspect the shooting occurred sometime over the weekend, but a better timeline will be developed based on the findings of the autopsies.

Police have no reported history of domestic violence from that residence and the only interaction with authorities was a noise complaint the family reported sometime ago concerning a party in the neighborhood.

There is no known motive, Vainuku said.

“We understand how frustrating it is for an incident of this magnitude to happen and to not understand why. We know people want to know why — we want to know why — but the truth is, we may never know,” she said.