MILWAUKEE (CBS 58) -- A former employee of St. Josaphat Parish School has now been charged after a student was accidentally hit by a bullet at the school on April 5. 

Heriberto Martin, 59, is charged with having a firearm on school grounds.

According to the complaint, Martin was a janitor at St. Josaphat Parish School. He admitted he brought his .380 caliber semi-automatic pistol to the school so he would have access to his tools and could fix an issue he'd been having with the gun's slide. Martin said the gun fired while he was working on it and the bullet traveled into a nearby classroom. 

The teacher who was inside the classroom at the time told police she heard a loud pop which she believed to be a gunshot. She said she determined a bullet came in through a wall about a foot from a student's head and passed through a second student's jacket and backpack before finally hitting a third student in the side where it only caused a small red mark. 

Martin said he later told the teacher what happened. 

The complaint says Martin stated he made a mistake and had no one to blame but himself. 

If convicted, Martin could spend three and a half years in prison and up to $10,000 in fines.