A "heroic" high school resource officer took down a campus shooter who opened fire inside a crowded gymnasium, authorities said Wednesday.

Matt Milby, a 19-year-old former student who had recently been expelled from Illinois' Dixon High School, allegedly fired several shots near the gym where seniors were practicing for their graduation ceremony, according to local reports.

He was confronted by Dixon Police Officer Mark Dallas, who chased him and shot him in the shoulder, authorities said. No one else was wounded in the incident. The teen allegedly fired at Dallas while running away.

"I could not be more proud of the police officer and the way he responded to the situation," said Police Chief Steven Howell. "With shots ringing out through the hallways of the school, he charged towards the suspect and confronted him head on," Howell said.

“Because of his heroic actions, countless lives were saved. We are forever indebted to him for his service and his bravery.”

Milby was taken into custody and is receiving treatment for his non-life-threatening injury, SaukValley.com reported.

Dallas' actions were markedly different than those of a Florida school resource officer who was criticized for acting too slow in a campus shooting that left 17 dead.

President Trump slammed Scot Peterson as a coward for failing to confront shooting suspect Nikolas Cruz at Marjory Stoneman Douglas High School in Parkland. Surveillance video showed Peterson outside the building where Cruz allegedly fired round after round from an AR-15 assault-style rifle.

Cruz has been behind bars since the Feb. 14 carnage. He faces 17 charges of first-degree murder. 

Peterson retired after the shootings and is receiving a monthly state pension of $8,702.35, The Sun Sentinel reported Wednesday.

RELATED STORIES 

Waffle House Hero Meets With Parkland Shooting Survivors

Father of Parkland Shooting Victim Said He Doesn't Want Cruz's Inheritance Money

Parkland Shooting Suspect Nikolas Cruz Will Donate His Inheritance to Charity: Lawyers