If the Serpentine Belt Breaks, What Exactly Happens?

One of my friend learned this the hard way. His belt snapped and got a hold of the radiator hose and broke it. The antifreeze coolant drained out and it over heated the car. Honestly, it was his fault. He does not stay on top of his maintenance as it was long over due to replace the belt. Also, when the belt snapped, he did not pull over and stop. He wanted to make it home. His $15,000 car has a busted engine now. Maintenance is a lot cheaper!