The three victims and another student who was injured in the attack knew one another and apparently had been having a small party that night, Laramie Police Commander Dale Stalder said.
Investigators were still trying to piece together what happened in the home early Sunday, but Stalder said they believe everyone involved had been accounted for and were considering the possibility it was a murder-suicide.
"There were several different kinds of weapons used," Stalder said. "This was a very violent criminal act."
He declined to release further details. Autopsies on the three were being performed Monday.
The dead were identified as University of Wyoming students Justin R. Geiger, 20, of South Beloit, Ill., and Amber N. Carlson, 19, of Denver, and Laramie resident Adam Towler, 20, who attended Emory University in Atlanta but was home visiting.
University of Wyoming student, Anthony N. Klochak, 19, of Chardon, Ohio, was treated at a hospital for minor injuries and released.
Klochak and Geiger shared the house with three others, who were elsewhere at the time, Stalder said. He said Kolchak was cooperating with investigators.
Neighbors called police at about 2 a.m. Sunday after hearing Klochak yelling for help a couple of blocks south of the campus.
University of Wyoming President Tom Buchanan issued a statement Monday saying he was shocked and saddened by what had happened.
"Our thoughts and prayers go out to the families and friends of all the victims of this tragedy," Buchanan said. "The University of Wyoming community will come together to do whatever we can to ease their burden in this difficult time."