Authorities: Las Vegas shooting suspect died 3:56

(CNN) -- The gunman who killed three people Wednesday at the University of Nevada, Las Vegas (UNLV), was a 67-year-old college professor, according to a law enforcement source. And investigators are looking into the possibility that he might have been ruled out for a job at the university.

The gunman died at the scene after a confrontation with police outside a university building, according to Las Vegas Metro Sheriff Kevin McMahill. He was identified as Anthony Polito, that source and another law enforcement source said.

The law enforcement source told CNN that the investigation's theory of a possible motive is that Polito sought a job at UNLV but was not hired.

He had worked for schools in Georgia and North Carolina, a law enforcement source told CNN. Polito's LinkedIn page lists his most recent full-time employment as a business professor at East Carolina University, a position he ended in 2017.

The shooting began shortly before noon on the fourth floor of the university's Beam Hall business school building, where students and faculty were preparing for final exams next week, the sheriff said. Outside, students were gathered for an event with games, food and a Lego building activity, he said.

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The gunman moved through several floors before getting into an armed standoff with law enforcement outside, who took the suspect into custody, according to the sheriff. It's unclear how the attacker died.

  • University of Nevada Shooting Leaves at Least 3 Dead; The suspect, who was a teacher, also died

In addition to the three people killed by the gunman, another was seriously wounded by the gunfire, but her condition was later stabilized at a hospital, according to McMahill. Four other people were also taken to hospitals due to symptoms of panic attacks, he added.

Authorities have not released the names of the victims or revealed whether they are students or staff members.

"Today we saw a lot of fear on the faces of those young men and women at UNLV," the sheriff said.

The shooting prompted a campus-wide shelter-in-place order as authorities scrambled to apprehend the gunman and then worked methodically to clear and evacuate Beam Hall and nearby buildings, McMahill said, noting that they found groups of students huddled behind many of the doors.

Students eagerly sheltered in the student center across the street from Beam Hall, hearing gunshots and then waiting for police to evacuate them, one student, who declined to be named, told CNN affiliate KVVU. "A lot of people panicked," he said.

"We all walked out of the building, hands up," the student said. "We were evacuated from the student center. We walked past one of the windows, the window was holey, there was glass everywhere."

Fear and panic on campus evoked memories of the Route 91 Harvest music festival massacre that devastated the city in 2017, and which remains the deadliest mass shooting in modern U.S. history. Wednesday's tragedy represents the 80th school shooting in the United States so far this year, 29 of which have occurred on college and college campuses, according to a CNN analysis.

The university has canceled all classes until Sunday, but is still considering how the campus will operate next week when final exams begin, UNLV Chancellor Keith Whitfield wrote in a message posted Wednesday on the university's website.

"Today is a tragic day for UNLV," Whitfield wrote. "We are all still in shock as we process the unfathomable event."

"I am mourning the victims of today's senseless shooting, and my heart breaks for the many students, faculty, staff, parents, loved ones, and community members who suffered during hours of painful uncertainty as officers made sure our campus was safe and secure again," the university's chancellor added.

U.S. President Joe Biden expressed his condolences to the families affected by Wednesday's shooting in Las Vegas and this week's massacre in Texas. He also called on Republicans in Congress to work with Democrats to pass a ban on assault weapons and high-capacity magazines.

"Together, we must do more to prevent more families, and more communities like Austin, San Antonio, and Las Vegas, from being torn apart by gun violence," Biden said.

"It seemed like all the cops in Las Vegas were at UNLV."

Police began receiving reports of a shooting at the university around 11:45 a.m., prompting law enforcement, both on-duty and off-duty, to rush to campus, the sheriff said.

Campus police also responded to the scene and confronted the suspect outside Beam Hall, where students had gathered for food and play moments earlier, McMahill said.

"Had it not been for the heroic actions of one of the responding police officers, there could have been countless additional lives," he said.

Police evacuated students after a shooting at the University of Nevada, Las Vegas, on Wednesday. (Credit: K.M. Cannon/Las Vegas Review-Journal/Tribune News Service/Getty Images)

A student was sitting outside eating breakfast when the shooting began, he told CNN affiliate KVVU.

"I heard three loud bangs and I was like, 'Oh, what was that?'" the student said. "The police showed up, so I ran inside.

"After two minutes, more gunfire. I ran to the basements, and I was there for 20 minutes," the student said. "I heard a lot of gunshots."

At Beam Hall, a teacher stopped mid-class after a loud noise echoed through the building, said student Brett Johnsen, who was in a second-floor classroom. But the sound didn't initially sound like gunfire, so the teacher resumed class.

"Then an alarm went off," Johnsen said. "I've never heard an alarm like that, it didn't sound like a fire alarm."

Students in the class began to pick things up, relatively calmly, Johnsen said.

"When we started to get out of class, that's when things got serious," she said.

Their teacher's gaze panicked and he urged the students to turn back, close the door, and drop to the floor.

"If the shooter walked into the classroom, we were all easy prey," Johnsen said.

A few moments later, the teacher opened the door to check that it was clear and told the students to run. Johnsen said he ran as fast as he could up the stairs of the building and went outside as far as he could. Everyone on campus was urging each other to flee and evacuate, he said.

"It seemed like all the cops in Las Vegas were at UNLV," Johnsen added.

The shooting evokes memories of the 2017 massacre

Parents Mabel Fontanilla and Raul Villalonga hug after a shooting on the campus of the University of Nevada, Las Vegas, on Wednesday. (Credit: Ronda Churchill/AFP/Getty Images)

The university is just minutes from the scene of the deadliest mass shooting in modern U.S. history: the shooting at the Route 91 Harvest music festival on Oct. 1, 2017, that left at least 58 people dead and hundreds injured. In the years after the massacre, two other victims died from shooting-related injuries.

Authorities investigating the UNLV shooting referred to the 2017 massacre several times during a news conference Wednesday simply as "Oct. 1."

Sheriff McMahill said the training Las Vegas authorities have undergone since Route 91 contributed to how quickly they were able to respond and apprehend the shooter at UNLV.

"After Oct. 1 and all the time, effort and energy that we've invested together — in training with the men and women of law enforcement, firefighters and emergency medical services — seeing how they've worked together seamlessly today made me very, very proud to be their sheriff." Said.

CNN's Cheri Mossburg, Sara Smart, Steve Almasy, Gillian Roberts, DJ Judd and Cindy Von Quednow contributed to this report.

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