CHARLOTTE (AP) — Students at University of North Carolina Charlotte were gathered for end-of-year presentations in an anthropology class when a gunman burst in and opened fire with a pistol, killing two and wounding four, a professor said.

New details emerged Wednesday about the previous day’s shooting that caused chaos and panic on the last day of classes at the University of North Carolina-Charlotte.

The shooting occurred during a class on the anthropology and philosophy of science, according to a message on what appeared to be the Twitter account of the instructor who witnessed the attack. Adam Johnson wrote that teams of students were delivering their presentations when the gunman opened fire.

“Yes, there was a shooting in my class today,” Johnson wrote. “My students are so special to me and I am devastated.”

Johnson declined to comment further Wednesday.

The motive wasn’t immediately clear for suspect Trystan Andrew Terrell, who UNC-Charlotte spokeswoman Buffy Stephens said had been enrolled at the school but withdrew during the current semester. Campus Police Chief Jeff Baker said Terrell had not appeared on their radar as a potential threat.

“I just went into a classroom and shot the guys,” Terrell told reporters Tuesday as officers led him in handcuffs into a law enforcement building.

Terrell, 22, was booked into the Mecklenburg County jail on two counts of murder, four counts of attempted murder, possessing and firing a weapon on educational property, and assault with a deadly weapon.

People reacting to the sound of gunshots and a campus alert scrambled to find safe spaces and endured a lengthy lockdown as officers secured the campus on the last day of classes. Hundreds were later marched out of buildings with their hands in the air before officers determined that the gunman appeared to have acted alone.

A vigil was planned for Wednesday evening, and the governor vowed a hard look to see what can be done to prevent future attacks.

“A student should not have to fear for his or her life when they are on our campuses,” Gov. Roy Cooper told reporters Tuesday.

In a news release, UNC-Charlotte said all the victims were students, five from North Carolina and one international. Riley C. Howell, 21, of Waynesville, and Ellis R. Parlier, 19 of Midland, were killed in the attack. Those injured were Sean Dehart, 20, and Drew Pescaro, 19, both of Apex; Emily Houpt, 23, of Charlotte; and Rami Alramadhan, 20, of Saihat, Saudia Arabia.

University Chancellor Phillip Dubois said in radio interviews Wednesday that three of the four wounded, previously described as having critical or life-threatening injuries, had undergone surgery.

The suspect’s grandfather, Paul Rold of Arlington, Texas, said Terrell and his father moved to Charlotte from the Dallas area about two years ago after his mother died. Terrell taught himself French and Portuguese with the help of a language learning program his grandfather bought him and was attending UNC-Charlotte, Rold said. But Terrell never showed any interest in guns or other weapons, and the news he may have been involved in a mass shooting was stunning, said Rold, who had not heard about the Charlotte attack before being contacted by an Associated Press reporter.

“You’re describing someone foreign to me,” Rold said in a telephone interview Tuesday night. “This is not in his DNA.”

Monifa Drayton, an adjunct professor, was walking onto campus when she heard the shots. She said she directed students fleeing the scene to take cover inside a parking deck.

“I heard one final gunshot and I saw all the children running toward me,” she said. “We started to get all the children pulled into the second floor of the parking deck and the rationale was if we’re in the parking deck and there’s a shooter and we don’t know where he is, he won’t have a clear shot.”

The shooting prompted a lockdown and caused panic across the campus with more than 26,500 students and 3,000 faculty and staff.

Spenser Gray, a junior, said she was watching another student’s presentation in a nearby campus building when the alert about the shooting popped up on everyone’s computer screens.

She said she panicked: “We had no idea where he was … so we were just expecting them at any moment coming into the classroom.”