Belayer was on the ground belaying his partner up the wall on a reasonably easy top rpe climb for the climber's skill set. The climber fell off the climb unexpectedly and, in a panic, the belayer did not lock off by holding the excess rope down by his hip to use the leverage of the ATC belaying device, but let go and instead grabbed the other end of the rope coming our of the ATC and up towards the climber. The belayer was successful in stopping the climber from falling all the way down the wall, but suffered extreme rope burn on his hands as a result of his actions.