A man who once applied for a professorship at the University of Nevada, Las Vegas allegedly opened fire on the campus Wednesday, killing three and injuring another in a shooting that shattered the peace at the school, officials said.
"What happened today is a heinous, unforgivable crime," Sheriff Kevin McMahill said during a news conference.
The suspect, identified by ABC News sources as Anthony Polito, 67, went floor to floor in UNLV's Beam Hall until he was stopped by campus police officers, authorities said.
The officers engaged the suspect in a firefight, where he was struck and killed, according to the police. The gunman has not been named by law enforcement.
MORE: UNLV shooting suspect Anthony Polito applied for professor job, wasn't hired: SourcesThree people were killed and a fourth gunshot victim was taken to Sunrise Hospital & Medical Center in critical condition, authorities said. Their condition was later upgraded to stable, police said.
Polito had applied for a college professorship at UNLV, but was not hired, sources told ABC News.
Investigators have now determined that the victims killed were faculty or staff, not students. That suggests to detectives that the rampage may not have been random, but may have been an attack that targeted certain people because of some sort of previous relationship or interactions.
Four people were transported to the hospital suffering panic attacks, according to McMahill. Some law enforcement officers sustained minor injuries in the incident, he said.
UNLV student Mike Henderson told ABC News that he was in a hallway when the shooting started and immediately ran into a classroom and sheltered in place.
He said he was later escorted out by police and saw someone with their face down, bleeding.
"[It’s] not something I thought would ever happen to me," he said.
MORE: Suspect ID'd in Texas shooting spree that left 6 dead, 3 injuredAuthorities said there is no further threat to the university, which has been closed for the rest of the week.
In a message to the UNLV community on Wednesday night, university President Keith Whitfield said, "We're all still in shock as we process the unfathomable event."
"My heart aches for our UNLV family. I know all of us are sending our love and support to the victims, their families, and friends during this difficult time," he said.
President Joe Biden said he was "praying for the families" and praised the "courageous" officers. The president again called on Congress to pass gun safety laws.
ABC News' Aaron Katersky, Molly Nagle and Fritz Farrow contributed to this report.