Former student used mother's gun in high school shooting: Police

The 19-year-old who allegedly opened fire in an Illinois high school this week used a gun that had been purchased by his mother, according to Illinois State Police.

No victims were injured in the Wednesday morning shooting at Dixon High School, and the suspect, Matthew Milby of Dixon, Illinois, is in custody.

The weapon used was a 9mm semi-automatic rifle that was purchased by Milby's mother in 2012, according to the state police.

The state police said it is investigating how the 19-year-old -- a former student at Dixon High School -- obtained the gun.

Milby allegedly fired several shots near a gym Wednesday morning.

Senior Devin Scott said he was in the gym when he heard what sounded like fireworks.

"It was a little unreal," he told ABC News.

The weightlifting coach then ran into the gym and alerted the students -- who were all seated in the bleachers for graduation practice -- to run for safety, Scott said.

"Some started crying as they started running," Scott said.

The school resource officer confronted the suspect who started running away, Dixon police said. When the officer pursued him, the suspect shot several rounds and the officer then returned fire, hitting the gunman, police said.

Milby was hospitalized for non-life-threatening injuries and then released from the hospital on Thursday, state police said.

He was taken to Lee County Jail to await his arraignment, which is set for today. Milby has been charged with three counts of aggravated discharge of a firearm, Dixon police said Wednesday. Bond was set at $2 million.