the photographer believed by repeatedly flashing his camera, he could alert the subway driver.
I dunno... at the very least, he should have been trying to yank that dude out until the last possible second. The line about using his camera to alert the driver sounds weak.
I'm not going to defend the photographer, but there was probably nothing he could go.
The pusher pushed him at the train signal, so you've got 5 - 15 seconds from there, the train was going at 35-40 mph till it's a few feet out from the start of the platform, someone might be able to figure the rate of deceleration, the car is about 70 feet long, 85000 pounds.
Almost everyone was 25 -30 feet down the platform, the guy had scared everyone but Han down that far. So you'd have to see the push, let it register in your mind, wait for Han to recover from the drop, etc.....
Lastly, and this is the scariest one, you could get pulled into the train path by the person in trouble. Think about it, most folks in trouble pull people toward them when being rescued, etc....
Photographer is a douche for offering the photo, but I don't think he could've done anything much.
Also, one interest thing I learned is that there is actually a light signal that might make the motor man stop if he sees it, not a flash, but a side to side light beam movement like nodding "No". That is the one sometimes used by track workers in emergency.