Investigators say Maurice Stewart, 15, fired the shot that killed a 35-year-old man on the platform at the Mount Eden Station on Monday.
The shooting injured five other people, including a 14-year-old, who police believe was another shooter.
Police also charged a 16-year-old.
35-year-old Obed Beltran-Sanchez, was killed.
"One bullet hit him in the chest. He died almost immediately," said Jorge Islas, Consul General of Mexico in New York. "And with that, that bullet, life on a dream, someone who was willing to do something important for his family."
Islas says Beltran-Sanchez left behind a wife and two young daughters. It is believed he was a migrant from Mexico who crossed the border from Canada in search of construction work as a day laborer.
"He can buy a little house for his family. And he was willing to work hard in American New York, and over time, retire and go back to Mexico to work on Puebla and eventually live in the house that he was willing to build," Islas said.
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