A former student opened fire on the campus of the University of North Carolina at Charlotte on Tuesday night, killing two people and critically injuring four other students. Officers quickly raced over and disarmed the suspect.

The shooting  caused widespread panic across campus as students scrambled to take shelter. Authorities went through campus buildings looking for students and staff sheltering in place. An alert told students to follow officer commands and for others to stay away from campus until an all clear is given.

“Just loud bangs. A couple loud bangs and then we just saw everyone run out of the building, like nervous, like a scared run like they were looking behind,” said Antonio Rodriguez, 24, who was visiting campus for his friend’s art show.

According to police, the shooting started at about 5:40pm in a classroom. Tristan Field, a student who witnessed the shooting, told CBS News that about 50 students tried to escape through two doors.

“A chair fell in front of the door, so people were tripping over that, like, trying to climb over it,” he said. “Some people fell down. It was like water through a funnel but wasn’t fast enough.”

Police disarmed and detained the suspect in the room where pistol shots rang out, according to Jeff Baker, campus police chief at the University of North Carolina at Charlotte. The Charlotte-Mecklenburg Police Department identified the suspect as Trystan Andrew Terrell, 22. He was charged with two counts of murder and four of attempted murder. According to the The Charlotte-Mecklenburg Police Department, the suspect acted alone. The suspect’s motive and identity of the victims are unknown.

To reunite students with their families, police told people to meet in a shopping center directly across the street from the campus. The campus remained closed late Tuesday, but police took  students to the buildings to retrieve their belongings.

“This is the saddest day in UNC Charlotte’s history,” the school’s chancellor, Phil Dubois, said in a letter to the community posted on the school’s website. “Families of the deceased victims are being notified and university staff are with those who are injured.”

A vigil was planned at the school for Wednesday.

A Waka Flocka Flame concert at the school’s football stadium was scheduled for 6 p.m. local time, shortly after gunshots were reported.The concert was cancelled and the rapper reported himself safe.