The MAC 90 7.26 MM assault rifle used by a 13-year-old male student in a shooting this morning at Joplin Memorial Middle School appeared to have jammed after the first shot.

Joplin police Sgt. Curt Farmer said the gun was a semi-automatic assault rifle, and that it is legal to possess. Rifles altered to fire in automatic mode are illegal.

“It is my understanding that the gun did jam after the first shot had been fired,” Farmer said.

The student entered Memorial Middle School shortly before 7:45 this morning, wearing a full-length, black, military-type black trench coat, Farmer said. The boy was wearing a makeshift mask made out of a white T-shirt.

The student was confronted in a hallway by Assistant Superintendent Steve Doerr, who saw the boy pointing the rifle at another student. He attempted to intervene, and called 911.

Memorial Principal Steve Gilbreth then confronted the boy, persuading him to leave the building. Gilbreth followed the boy out, walking about 10 feet behind him.

Police arrested the student at Ninth and Wall streets, the old Joplin Public Library.

Inside a backpack he was carrying, Farmer said, police found a set of BDUs, or camouflage battle dress uniforms. Police also found notes on how to make a bomb.

Earlier today, the Springfield Bomb Squad established at command center at 521 S. Gray Ave. in Joplin. Police searched the home, as well as the third floor of the middle school. The results of those searches were not immediately known .

Tiffany Pendergraft, 12, a seventh-grader at Memorial Middle School was eating breakfast in the cafeteria when the school was locked down. “I was in the middle of breakfast,” she said. “They started saying we got to be quiet. I was just kind of wondering what was happening.”

She said she was “sort of” scared, but she and a friend also joked with each other morbidly about what the other would do if one was killed.