stormtrooper armour at endor

They may not have been killed... just knocked unconscious or pushed back. The rocks were of a fair size, and were dropped from pretty high (the gliders and off that ridge/tree thing). I always saw the Stormtrooper armour as being strong enough to block the force of a bullet, but not something like a blaster bolt. Whilst the armour wouldnt be too damaged by the rocks, the kinetic energy would sure pack a punch! (this is of course ignoring the crack in one of the stormies' helmets... but that was there before the rocks hit him)