A video shows terrified people being directed to evacuate a University of Nevada, Las Vegas building as police responded to an active shooter on Wednesday.

Crowds of students ran for their lives after a gunman attacked the campus on Wednesday morning, killing three people and critically wounding a fourth. 

Police later identified the gunman as 67-year-old Anthony James Polito, a resident of nearby Henderson, Nevada. Authorities say Polito had applied for several jobs at various colleges and universities in Nevada but was rejected each time. 

Polito was killed by police during a shootout Wednesday. 

LAS VEGAS POLICE IDENTIFY SUSPECT, VICTIMS, IN UNLV SHOOTING THAT LEFT 3 DEAD AND ONE INJURED

Clark County Sheriff Kevin McMahill told reporters Thursday that Polito had a list of targets at the school and more than 150 rounds of ammunition. The list included faculty at his former place of employment in Eastern Carolina University in North Carolina.

"None of the individuals on the target list became a victim," McMahill said, adding that police have contacted everyone on the suspect’s list, except for one person who is on a flight.

Polito also mailed 22 letters to various university employees across the country with no return address, one of which had a white powdery substance inside, McMahill said.

When Polito's home was searched after the shooting, detectives found a chair with a downward-pointing arrow to a document similar to a will and testament. Authorities also said Polito appeared to be struggling financially, as detectives found an eviction notice taped to the door of his apartment. 

'ACTIVE SHOOTER' AT UNIVERSITY OF NEVADA, LAS VEGAS WITH 'MULTIPLE VICTIMS;' SUSPECT DEAD

Investigators have not yet announced a motive in the shooting.

Terrified students and professors cowered in classrooms and offices as the gunman roamed the top three floors of UNLV’s five-story Lee Business School around lunchtime Wednesday.

The horror began about 15 minutes after Polito arrived at UNLV in a 2007 Lexus at around 11:30 a.m., McMahill said. Police received the first reports of an active shooting at 11:45 a.m.

Everything happened in about 10 minutes. Polito made his way through the building and killed three people: Patricia Navarro, an assistant professor at UNLV's accounting department; Cha Jan Chang, a professor at the university's business school; and a third unidentified victim. A fourth victim was injured and is in life-threatening condition, McMahill said. 

UNLV SHOOTING SUSPECT WAS PROFESSOR WHO HAD APPLIED FOR JOB: AP SOURCE

Police stopped the attack at around 11:55 a.m., when two police detectives confronted Polito outside the building as he left the business school. The detectives fired their weapons at the alleged shooter, leaving the suspect dead. 

Officials said that Polito used a Taurus 9mm handgun, purchased legally in 2022, adding that 11 magazines were with the individual when he came to campus.

UNLV is home to some 30,000 students. The sheriff said students had been gathered outside the building and in the student union to eat and play games during the attack. If police had not intervened and stopped the attacker, "it could have been countless additional lives taken," McMahill said. 

It is unclear how long Polito has resided in the Las Vegas area. A statement from East Carolina University said he had resigned as a tenured professor there, The Associated Press reported.

Paul Whittington, one of Polito's former students, told The Associated Press in an interview that that Polito seemed obsessed with anonymous student reviews left at the end of each semester.

He said that Polito told the class that he remembered the faces of students who gave him bad reviews and would express that he was sure who they were and where they sat, pointing at seats in the classroom. 

"He always talked about the negative feedback he got," Whittington said, recalling his time in Polito's intro to operations management class in 2014. "He didn’t get a lot of it, but there would always be one student every semester, or at least one student every class, that would give a negative review. And he fixated on those."

Fox News Digital's Adam Sabes and The Associated Press contributed to this report.