A conductor at the South Station Commuter Rail Station told authorities that he was trying to help a female passenger just after 11 p.m. on Friday, July 23, when the attack happened, transit police said.
He asked where the woman was going to make sure she was on the correct train, but the teenager took offense. He pulled out a knife and demanded to know, "Why you talking to my shorty?" authorities said. The conductor ran off the train to call for help.
The teenager thought he was in the clear when officers arrived because of his age. He was shocked when they put him in handcuffs.
"You can't arrest me. I'm 17!" he told the officers, transit police said.
Officials charged him with assault with a deadly weapon. Police did not release his name because of his age.
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