Colin Kingston, 24, of Geneseo was distraught because his girlfriend of three years, Kelsey Annese, had recently broken up with him, Geneseo Police Spokesman Jeffrey Szczesniak said at a press conference.
Early Sunday morning, Kingston telephoned his father and said he'd "brought harm" to Annese, Szczesniak said.
The father called police, who went to Annese's residence on the second-floor of a house converted into apartments that were mostly occupied by members of the women's basketball team, Szczesniak said.
Officers found the bodies of Kingston; Annese, 21, of Webster, New York; and Matthew Hutchinson, 24, of Vancouver, British Columbia.
No sign of struggle
Szczesniak said there were no signs of forced entry or a struggle, indicating Kingston may have surprised Annese and Hutchinson. He didn't know the nature of the relationship between Hutchinson and Annese.
Kingston had bought a large knife at a retail store and police think he used that in the killings, Szczesniak said.
Investigators think the killings happened between 5:30 a.m., when officers ticketed cars on the street and didn't see Kingston's vehicle, and 6:21 a.m., when Kingston called his father, Szczesniak said.
"When the phone call was terminated by Colin, shortly thereafter Colin Kingston took his own life," Szczesniak said.
Szczesniak said Kingston had "made some suicidal comments to several people, but there was no actual threats to harm Ms. Annese or anybody else."
Students at the school of about 5,000 were returning to campus after winter break.
"It will likely be very difficult for many to face a new semester with this tragedy on their minds," college President Denise A. Battles said. "We have experienced a terrible tragedy in Geneseo today involving members of our community."
SUNY-Geneseo is a picture-book campus in a historic part of New York state.
Classes to resume Tuesday
"Nestled next to the Village of Geneseo -- one of 24 communities nationwide to be recognized as a National Historic Landmark -- the campus' ivy-covered brick buildings evince a traditional college ambiance," the college website says.
The website said
Annese was a senior and a member of the women's basketball team who was an education/Spanish major with a psychology minor.
Hutchinson, a senior, was a member of the hockey team who was majoring in geography. He belonged to the Geneseo Volunteer Fire department.
"I can say that Matt was really in the upper echelon of our department," Geneseo Fire Chief Andrew Chanler told CNN affiliate WIVB
. "He was trained and qualified to perform all duties as a firefighter. He also held EMT certification, so really there wasn't anything that Matt couldn't do with us. So it's been very difficult for our department."
Kingston, who had previously played on the school basketball team, lived in Geneseo but had not registered for spring classes.
Classes will be held Tuesday but the men's and women's basketball games have been postponed.
"We think our students will be comforted by keeping as much stability in their lives as possible, even during a difficult period of mourning," Battles said.