Pellet guns are no big deal unless you are standing up in the train and can't tell if it's a pellet or a bullet.
Some people take kids throwing stuff at cars pretty badly. There was a kid shot and killed for tossing an egg at a car as it passed by in Indiana last year. The driver went home, loaded his gun and went back for revenge. A teenage boy playing a prank lost his life over that one.
My Mom once worked on the prosecution of some teenagers who threw a water balloon off an overpass. It killed a driver.
Yeah, I know. It's just that they seem more edgy than usual.