Look here. This says the doors to the Boston subway train closed on her purse, and she ran down the platform to try and get it from between the doors, only to slam into the wall as the train entered the tunnel. Get the video here. Image shown below is the woman right before the train left.
As an aside, almost the same thing happened to me on BART. Sitting there in the train, waiting for the doors to close. They start to close, and as they do a little old lady comes zooming down the stairs, onto the platform, and makes a lunge for the doors..with her bag of Chinese food. She swings it through the doors. Like the styrofoam containers will stop heavy pneumatic doors. Doors slam shut, and her bag of Chinese food is stuck in the door, facing inside, just suspended in mid-air. So since I am parallel to the doors, everone looks at me as the train rolls off, leaving the little old lady behind. I just pull the bag down, have a Spring Roll, and call ahead to my wife to let her know I picked up dinner in The City.