When police went to his house later that day, they a number of improperly secured rifles and handguns, along with ammunition.

Millbury Police Chief, Donald Desorcy said he's certain the teacher knew he was carrying ammunition when he walked into school on Thursday, even though the man claimed it was an accident.

"He explained to us that he had been out shooting the day before and apparently had these rounds, these magazines, in his clothing, and apparently he wore the same clothing to school yesterday," Desorcy said.

A substitute teacher has been fired after police say he brought .9 mm ammo to a preschool class. His explanation to officers at 4 on @boston25 pic.twitter.com/HmtxeFtz6i — Kathryn Burcham (@kathrynburcham) April 12, 2019

The teacher was licensed to carry and his weapons were registered, but his license has now been revoked under the police chief's discretion.

"To me, that’s just not sound judgment, an individual not thinking clearly or have a strong concept of gun ownership or gun responsibility," said Desorcy.

Police said they aren't identifying the man because he has not been criminally charged. He has, however, been fired from the district.