[1.4.5] NPC disappearing when hitting player

[Lungi]

Not sure if there's a way to do this, but in one of my levels, there are npc-58 (NPC block) generators, and the NPCs hurt you when they fall. I'm trying to make the NPC disappear/die if it hits you from above (falls on you), but act as a block from the top and sides. Is there any way to do this (with NPC codes or scripts)?