Jose Lara was trespassing at a construction site near South Station just before 1 p.m. on Tuesday, July 12, MBTA Transit Police said.
When two workers asked him to leave the garage where they were working, Lara lashed out and punched them before running away, police said. He threw down his book bag as he fled.
MTBA officers tracked him down to Keeland Street shortly after the attack. When they searched that bag, they found a 9mm ghost gun with a large-capacity clip and several bullets, officials said.
Ghost guns don't have serial numbers and are untraceable. Officers arrested Lara and took him to the Transit Police Department's headquarters for booking.
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