A 12-year-old Chicago boy was arrested Tuesday after he showed up at school with three rounds of ammunition in his pocket and a handgun in his backpack, MyFoxChicago.com reported.

The boy was arrested at Bethune Elementary School at 3:25 p.m. local time and was charged as a juvenile with unlawful use of a weapon, police were cited by MyFoxChicago.com as saying.

Students alerted the school’s dean that the boy had a handgun in his bag, according to the police report, MyFoxChicago.com reported.

Police said the dean found a 9mm Ruger handgun inside the boy’s backpack, MyFoxChicago.com reported. Three live .380 caliber rounds of ammunition, which did not match the Ruger handgun, were found in the boy’s pants pocket, police said according to the site.

Police are investigating the incident.

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