Michigan State University student Dominik Molotky was in class on Monday evening when he heard a gunshot in the hallway, just outside the door.
"I was sitting next to the nearest door and thank god that my fight-or-flight response kicked in because, right when that first gunshot went off, I booked it to the far corner of the class," Molotky, a senior, told ABC News in an interview Tuesday on "Good Morning America."
A couple seconds later, the gunman entered the classroom and fired "three to four more rounds," Molotky said.
"I was ducking and covering," he recalled. "I think one of the students in my class got hit."
When the gunfire stopped for "30 seconds to a minute," Molotky said, he and his classmates started breaking open a window so they could escape.
"There was glass everywhere," he added. "We broke open the window and climbed out of there, and I booked it back to my apartment."
Molotky and other students recounted their horrifying experiences as the mass shooting unfolded at multiple locations on MSU's main campus in East Lansing, Michigan.
Michigan State student details experience during deadly campus shooting
Dominik Molotky was attending class on campus when a gunman opened fire on Monday evening.
ABCNews.com