CHICAGO (CBS) — Students at Foreman High School in the Belmont-Cragin neighborhood were likely looking forward to the last day of school upon arriving Friday, but instead they ended up on lockdown someone brought in a gun.

The 16-year-old boy is now awaiting criminal charges.

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The teen, a self-admitted gang member, arrived at the school, 3235 N. LeClaire Ave., around 9 a.m., police said.

He had been expelled from the school, but tried to get in Friday morning. Officers recovered his book bag, which had a loaded semi-automatic handgun inside, police News Affairs Officer Laura Kubiak said.

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Police said the teen was attempting to pass on the gun to another student.

The teen was arrested and charges are pending, police said.

It was the last day of school when the incident occurred.

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The Sun-Times Media Wire contributed to this report.