DRIVING AT APPROX 35-40 MPH APPROACHING A HAIRPIN TURN TRIED TO BREAK AND VEHICLE DID NOT SLOW DOWN SLID THROUGH THE CORNER INTO A ROCK, PUT THE VEHICLE IS REVERSE AND PRESSED ACCELERATOR THE VEHICLE RPM INCREASED ON OWN TRIED TO BREAK THE RPM DID NOT DIMINISH(FOOT OFF ACCELERATOR) BEFORE I HAD TIME TO SHUT THE TRUCK OFF I HIT A TREE BEHIND ME. IT APPEARS SOMETHING STUCK IN ACCELERATOR (MECHANICAL) OR THE COMPUTER SYSTEM( ELECTRONICS) FAILED. THE VEHICLE HAS NOT YET BEEN TESTED.