A Central Massachusetts teacher faces charges of bringing more than 100 live rounds of ammunition onto school grounds, an alleged attempt to convince the school district to install more security measures within the building.

Southbridge High School was placed on lockdown Thursday morning after Alfred J. Purcell, a teacher at the school, reported he found a live round of ammunition in a school stairwell.

During the lockdown, school officials reviewed video camera footage captured Thursday morning before Purcell reported finding a bullet.

On the video footage, Purcell is seen standing in the stairwell, removing the bullet from his pocket and dropping it on the ground, according to police. About 10 minutes later, police say he returned to the stairwell, took a picture of the bullet then requested assistance on his school radio.

The teacher was arrested on school grounds. While speaking with officers during the booking process, he reportedly admitted to dropping the live round in the stairwell, seeking to “prove to the school that they needed to get metal detectors.”

Southbridge police said the “faint odor of an alcoholic beverage emanating from his breath but he denied consuming any alcoholic beverages.”

After Purcell was arrested, police searched his vehicle. Just over 100 live rounds of 20 gauge shotgun ammunition were found in the trunk of his vehicle.

Purcell, a resident of Woodstock, Conn., has a license to carry in Connecticut but not Massachusetts.

He was charged with two counts of the unlawful possession of ammunition, two counts of carrying ammunition on school grounds, disturbing a school assembly, disorderly conduct and disturbing the peace. He is scheduled to be arraigned in Dudley District Court on Thursday.