Three people were killed and another critically injured in a shooting at a Las Vegas university on Wednesday, with the suspect also dead. Police say that campus police officers shot the gunman after a brief standoff with them. It’s the latest mass shooting in a country that is grappling with gun violence, with no end in sight.

The shooting at the University of Nevada, Las Vegas, sent students and professors running for cover. They barricaded themselves in classrooms and dorm rooms while authorities rushed to the scene. The first reports of shots fired came in at 11:45 a.m., and alerts went out across the campus of 30,000 students and faculty members.

Police swarmed the campus just a few miles from the world-famous Las Vegas Strip. They closed off buildings, and the Federal Aviation Administration put a ground stop on flights near Harry Reid International Airport. It was lifted a few hours later.

A university statement said that law enforcement had “immediately engaged the suspect in a shootout” and that he is dead, adding that police did not immediately identify the victims or have any information on a possible motive. Police Chief Adam Garcia said he was heartbroken by the shooting but applauded the actions of campus police, who shot and killed the suspect. “If it weren’t for the heroic actions of our brave campus police, there could have been countless additional lives lost,” he said.

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Professor Kevaney Martin took cover under a desk in her classroom, where other faculty members and students hid for hours until they were told to evacuate. She texted friends and loved ones, hoping to receive word that a suspect had been detained. When another professor came to the room and told them to leave, they joined dozens of others rushing out of the building. Martin had her students pile into her car and drove them off campus.

Matthew Felsenfeld, 21, said he and about 12 classmates barricaded themselves in a building near the student union. He said he heard several rounds of shots, followed by what sounded like a gun’s reloading. “That’s when you know this is something real,” he said.

A medical center says it received three patients from the university but didn’t immediately have their conditions or a list of injuries. One patient was in critical condition, and the other two were in stable condition, hospital spokesman Chris McMahon said.

Authorities haven’t released a suspect’s name, but they have described him as a man in his 60s who was a college professor. He had been a lecturer in the School of Criminal Justice and Security Studies.

Earlier, Sheriff Kevin McMahill of the Las Vegas Metropolitan Police Department wrote on social media that “the suspect in this #ActiveShooter incident is deceased.” The department said it would not release his name until family members were notified.