The anthropology professor whose classroom was the scene of a deadly shooting at UNC Charlotte Tuesday that killed two of his students and injured four others wrote a lengthy blog post on his experience on Thursday.

Adam P. Johnson — a graduate of Lee County High School and an adjunct professor of anthropology at UNC Charlotte for four years — was leading team presentations in the Woodford A. Kennedy Building at 5:40 p.m. Tuesday when 22-year-old Trystan Terrell began shooting a pistol at students. In his blog post, Johnson described the classroom (pictured) and the moments leading up to the shooting. He wrote:

The first presentation is a video on static versus dynamic universe. It is quite good, using a lot of data and contextualizing it in a cultural context. We get about seven minutes into the video and without warning, earsplitting bangs ring throughout the room, off the glass walls, creating a terrible reverberation.

Johnson said the shooter was a former student of his who dropped out in January (he refuses to name the student in his blog post). When the shots were fired, Johnson said students “in great confusion” began to run. One student later told him he thought it was part of the presentation and sounded like firecrackers.

Although he didn’t name him in his post, Johnson said he witnessed student Riley Howell tackle the shooter, adding that his actions likely saved several lives. In his post, Johnson called Howell a “hero.” Johnson, meanwhile, ushered students out of his classroom, according to his post, and picked up one student who fell on the way out. He and several students exited into the building’s foyer, then ran into the courtyard, surrounded by classrooms and office buildings. They yelled out “active shooter” as they ran — eventually reaching the anthropology department and locking themselves into an office before calling 911. He wrote that it took about four minutes (feeling like four hours) before police arrived.

He wrote:

Many of the students were able to quickly evacuate the room, but not all. Through discussions with victims, survivors, I was able to get an idea of what happened. Before opening fire, the shooter said nothing, did not indicate that they were going to shoot; simply raised the gun and started to fire.

It was all over in a matter of second. One student tackled the shooter and undoubtedly saved more lives. They are an absolute hero.

The shooter emptied the magazine, laid the gun down, and sat on the ground.

One victim asked the shooter to stop shooting and they said “I’m done.”

Johnson’s post goes into his experience interviewing police after the shooting, his thoughts on mass shootings in the U.S. and his prior experiences with the shooter before Tuesday’s tragedy.

We encourage you to read the entire post. Johnson said the post will serve as his statement to the media concerning the shooting.