TRUCK WAS PARKED IN GARAGE, FACING OUT OF GARAGE. TRUCK HAD NOT BEEN DRIVEN FOR 4 DAYS. TRUCK HAD HANDBREAK SET WHEN PARKED. I STARTED TRUCK UP DUE TO THE NUMBER OF DAYS IT HAD NOT BEEN DRIVEN TO CHARGE BATTERY. VERFYED THAT HANDBRAKE WAS SET ( RED BRAKE LIGHT WAS ON) AND PLACE TRUCK IN NEUTERAL (5-SPEED). (GARAGE DOOR WAS OPEN DUE TO TRUCK RUNNING). I WENT INSIDE AND ABOUT 5 MIN PASSED LOOKED OUT KITCHEN WINDOW SAW TRUCK AT END OF DRIVE WAY. TRUCK WAS STOPPED BY TOW HOOK HITTING TREE. DRIVER SIDE MIRROW HIT TREE AND WAS FOLDED BACK.