Pop. POP. POOOOOOOOOOOOOOOOOOOOOOOP. (I really like Pop)

Hypotechical situation here. Let's say there is a school bus full of kids hurdling down a bridge and it'll fall into the ocean where all the kids will slowly freeze to death, no survivors. Here is where the choice comes in. There is also a bomb on the bus, and you're given a button that, when pressed, will cause the bus to explode, killing everyone instantly and peacefully. There are some conditions, though, let the bus fall into the ocean and everyone will know you did nothing to help the kids, however, blow the bus up and no one will ever know you did it.

So, what do you do?