The 14-year-old was hit along the /*Long Island Rail Road*/ tracks in /*North Bellport*/ around 4:30 p.m.
The conductor reported seeing a group of teens on the tracks just before the accident.
It's not clear why they were there.
The victim was airlifted to /*Stony Brook*/ University Medical Center.
/*Suffolk County*/ police arrested a 13-year-old boy who was with the teen who was struck.
He was charged with criminal mischief for throwing rocks at cars from the train tracks.
