The University of Nevada, Las Vegas campus turned to chaos Wednesday when a gunman opened fire as he roamed the halls, killing three people and critically wounding a fourth.
It was later reported that all four people who were shot on campus were members of the school's faculty.
The gunman, who died in a shootout with police, was a 67-year-old career college professor who had recently — and unsuccessfully — sought a job with UNLV, according to a law enforcement official, The Associated Press reported. The shooter was identified as 67-year-old Anthony Polito.
Polito had career connections in other states, having previously worked for schools in Georgia and North Carolina, including East Carolina University, sources told CNN.
Police have his phone and were examining it for a possible motive, Scripps News Las Vegas reported.
Police said they found evidence the attack targeted specific individuals, and that the suspect did not appear to have targeted students.
The shooting happened just before noon local time on Wednesday, when Polito opened fire on campus on the fourth floor of Beam Hall, before moving to several other floors, police confirmed.
Police engaged Polito outside a campus building and killed him at the scene. Surveillance video displayed at a press conference on Thursday appeared to show Polito charging at a police officer before he was killed.
Police said they were not sure of the exact sequence of the shootings by Thursday, but were investigating the timeline further.
"If it hadn’t been for the heroic actions of one of those police officers who responded, it could've been countless additional lives taken," said Sheriff Kevin McMahill of the Las Vegas Metropolitan Police Department.
Police said the suspect sent various letters across the U.S. to college campuses, without a return address. The investigation was working with the U.S. postal service to further analyze those letters.
"We're still trying to determine a motive," McMahill said. He said the suspect had a list of what appeared to be targets, and police said they have contacted people on that list to determine if they "are alright," McMahill said Thursday.
Investigators found an eviction letter on the door of the suspect's home, McMahill said.
A surviving victim, who was shot, was hospitalized and later labeled as in stable condition, according to police.
It marked the deadliest shooting in Las Vegas since October 2017 when 60 people in total were killed after a shooter opened fire on a music festival from the Mandalay Bay hotel overlooking the Vegas strip. That was the deadliest mass shooting in modern American history.
"I'm trying to keep myself calm. This is my second shooting," said one unnamed person on campus at the time, who spoke to the media. "This is just more stuff in therapy to talk through."
The police investigation remained ongoing by Thursday.
The university called Wednesday's shooting "the most difficult day in the history" of the school, as it worked to honor the victims and help the student body, faculty and staff mourn losses.
UNLV President Keith Whitfield said the school was still working out what changes would be made to the academic calendar for the school through the rest of the year.
Trending stories at Scrippsnews.com