The suspect in the deadly shooting at the University of Las Vegas, Nevada (UNLV), had a list of targets at the school and at East Carolina University in North Carolina, police said.

Three faculty members were killed and a fourth was wounded by the gunman who opened fire on the campus before dying in a shootout with police, according to university officials.

Clark County sheriff Kevin McMahill identified the suspect as Anthony Polito, a longtime business professor. Before the shooting, the gunman mailed 22 letters to university faculty members across the US, but the contents of those letters was not immediately known, Mr McMahill said.

The sheriff said police have contacted everyone on the suspect’s list, except for one person who was on a flight.

Campus Shooting Las Vegas
A police officer at the scene of a shooting at the University of Nevada (KM Cannon/AP)

“None of the individuals on the target list became a victim,” Mr McMahill said.

The sheriff said investigators were still looking into a motive but noted that Mr Polito applied for “several” jobs at various colleges and universities in Nevada and was denied the job each time.

The suspect’s weapon was purchased legally last year, Mr McMahill said. Police were still investigating how many rounds were fired during the rampage.

University president Keith E Whitfield said in a letter to students and staff that the shooting in the building housing UNLV’s business school “was the most difficult day in the history of our university”.

He identified two of the victims who were killed as business school professors Patricia Navarro-Velez and Cha Jan “Jerry” Chang. Mr Whitfield said the name of the third victim will be released after relatives have been notified of the death.

Police outside an apartment in Nevada where the suspect in a fatal shooting lived
Police outside an apartment in Nevada where the suspect in a fatal shooting lived (Ken Ritter/AP)

The wounded man, a 38-year-old visiting professor, was downgraded to a life-threatening condition on Thursday, police said at a news conference.

Terrified students and professors cowered in classrooms and dorms as the gunman roamed UNLV’s Lee Business School on Wednesday and opened fire just before noon on the fourth floor, where faculty and staff offices for the accounting and marketing departments are located.

Investigators searched an apartment in nearby Henderson, Nevada, late Wednesday as part of the investigation and retrieved several electronic devices, including Mr Polito’s mobile phone, one of the officials said.

Mr Polito was a professor in North Carolina at East Carolina University’s Department of Marketing and Supply Chain Management from 2001 to 2017, according to a statement released on Thursday by the school. He resigned in January 2017 as a tenured associate professor.

One of Mr Polito’s former students at East Carolina University, Paul Whittington, said Mr Polito went on tangents during class about his many trips to Las Vegas. Mr Polito told his students he visited twice yearly, staying in different hotels and going to various clubs, Mr Whittington said.

APTOPIX Campus Shooting Las Vegas
Both local and campus police descended on the university (Madeline Carter/AP)

“He was really, really, really fixated on the city of Las Vegas,” Mr Whittington said. “I think he just really liked going there.”

The attack at UNLV terrified a city that experienced the deadliest shooting in modern US history in October 2017, when a gunman killed 60 people and wounded more than 400 after opening fire from the window of a high-rise suite at Mandalay Bay on the Las Vegas Strip, just miles from the UNLV campus.

Lessons learned from that shooting helped authorities to work “seamlessly” in reacting to the UNLV attack, Clark County sheriff Kevin McMahill said at a news conference.

After opening fire, the gunman went to several other floors of the business school before he was killed in a shootout with two university police detectives outside the building, which is next to the university’s student union, UNLV police chief Adam Garcia said.

Authorities gave the all-clear about 40 minutes after the first report of an active gunman.

It was not immediately clear how many of the school’s 30,000 students were on campus at the time, but Mr McMahill said students had been gathered outside the building and the student union to eat and play games. If police had not killed the attacker “it could have been countless additional lives taken”, he said.

Kevaney Martin, a faculty member at UNLV’s journalism school, said she took cover under a desk in her classroom, where another faculty member and three students took shelter with her.

Police at the University of Nevada, Las Vegas
The shooting happened at the University of Nevada, Las Vegas (John Locher/AP)

“It was terrifying. I can’t even begin to explain,” Ms Martin said. “I was trying to hold it together for my students, and trying not to cry, but the emotions are something I never want to experience again.”

Ms Martin said she was texting friends and loved ones, hoping to receive word a suspect had been detained. When another professor came to the room and told everyone to evacuate, they joined dozens of others rushing out of the building. Ms Martin had her students pile into her car and drove them off campus.

“Once we got away from UNLV, we parked and sat in silence,” she said. “Nobody said a word. We were in utter shock.”

Student Jordan Eckermann, 25, said he was in his business law class in a second-floor classroom when he heard a loud bang and a piercing alarm went off, sending students to their feet.

Some of his classmates ran out in panic, but Mr Eckermann said he peered outside the classroom first before leaving. He said he saw a law enforcement officer in a bulletproof vest holding a long gun, while clothing, backpacks and water bottles lay scattered on the floor.

Minutes later, when he was outside, Mr Eckermann said he heard bursts of gunshots coming from outside the business school, totalling at least 20 rounds.