Jake, I'm very sorry about what happened.
If anyone is reading, there are a few procedures one can follow to slow a vehicle when the brakes fail. I anyone has more, post them.
~~ Weave back and forth violently if there is no oncoming traffic. This will greatly slow your speed.
~~ Run off the road and sideswipe things to reduce speed.
~~ Drive off the road into a field. DO NOT drive into any trees larger than saplings.
~~ Use the emergency brake
~~ Downshift
~~ Turn the engine off unless the steering wheel locks when you do.
But no matter what you do chances are very good that it's going to b bad. The best you can hope for is to avoid catastrophic injury.
(BTW, IMO this should be in General Truck Talk)