They want your stuff. 
Your stuff is moving. 
Here’s what thieves might do.

When real thieves steal sheep tossed from the back of a truck, it looks like this:


Thieves Steal Sheep From Moving Truck

When real thieves try to steal from a moving vehicle and are filmed by a night vision camera on a helicopter, it looks like this:

Romanian thieves attempt a night heist, 
filmed by Romania’s Department 
for Organised Crime and Terrorism

When fake thieves steal an expensive sports car from a moving train as part of an $86 million dollar movie, the behind-the-scenes view looks like this. (But they also smash their own truck into the train and…)

Fast Five – Featurette: "Train Heist"