Three people were fatally shot Wednesday and a fourth person was critically wounded in an attack on the University of Nevada, Las Vegas campus, police said. The suspected shooter also was found dead.

The attack just before noon sent police swarming onto the campus, which is just a couple of miles from the world-famous Las Vegas Strip while students barricaded themselves in classrooms. Authorities gave the all-clear about 40 minutes after the first report of an active shooter.

Police haven’t released the identity of the shooter or the motive for the attack. The shootings took place in a city still scarred by an October 2017 attack by a gunman at the Mandalay Bay casino that killed 60 people and wounded hundreds more.

Police said in a post on X, formerly Twitter, that three people were killed and a fourth person was in critical condition at a hospital. Authorities didn't immediately provide additional information but planned to give further updates at a news conference scheduled for 5 p.m. PT.

Alerts went out across the campus after callers reported an active shooter to police at 11:45 a.m. Wednesday, said Adam Garcia, a university police official. He said officers found and “engaged” a suspect, who is now dead. It was not immediately clear how the suspect died.

Students and professors on the campus of 30,000 barricaded themselves inside classrooms and dorm rooms.

Student John Harris heard what he later realized was a gunshot as he was getting out of his car in the parking garage of an on-campus apartment complex. In the elevator, Harris said he got an emergency text alert text from the university.

“I wasn’t sure what to believe,” said Harris, 21, who ended up sheltering at a friend’s dorm. “But as I came down to the street, and I saw there were a bunch of cops in the parking lot at the student union, I knew what I heard was a gunshot and this wasn’t a drill.”

Professor Kevaney Martin took cover under a desk in her classroom, where another faculty member and three students took shelter with her.

“It was terrifying, I can’t even begin to explain,” Matin 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.”

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. Martin had her students piled 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.”

The university said on X that the shooter was at the Beam Hall, Frank and Estella Building, home of UNLV’s Lee Business School, and that police were responding to an additional report of shots fired at the nearby student union.

Las Vegas police posted on X that a suspect “has been located and is deceased” about 40 minutes after the initial alert was posted.

Students and the community were alerted to the emergency by a university post on X.

“This is not a test,” the university wrote. “RUN-HIDE-FIGHT.”

Student Matthew Felsenfeld said he and about 12 classmates barricaded their door in a building near the student union.

“It’s the moment you call your parents and tell them you love them,” said Felsenfeld, a 21-year-old journalism student.

He said he didn’t hear gunfire or see anyone injured but said he saw out the windows as police staged to enter the neighboring building. a short while later, police came and ushered them out.

Pierre Lescure, a UNLV senior, was riding his bicycle from home to campus for a meeting when he said about 10 police cars drove past him.

“They drove too fast and there was no ambulance, just cops. It was clearly a shooting,” Lescure said. “It could not be something else.”

UNLV’s 332-acre campus is less than 2 miles east of the Las Vegas Strip.

In response to the campus shootings, the Federal Aviation Administration issued a ground stop of all flights coming into Harry Reid International Airport. The university is roughly 2 miles north of the airport.

Tony Molinaro, an FAA spokesperson, referred a request to comment to Las Vegas law enforcement.

Classes were canceled at the university, and UNLV’s basketball game at the University of Dayton, Ohio, was canceled Wednesday night because of the Las Vegas shootings.