Headcrab Attack sequence

Hi guys,

I was looking through the scripted sequences and noticed there was a sequence with a NPC being attacked by a headcrab then falling to the floor with the headcrab attached to his face. I have fairly good understanding of how to script these type of seqences but have found that the headcrab simply rotates into a strange position inside the floor, instead of flying into the NPC's hands, i would really apprciate it if someone could tell me how to get this working, i believe the sequence is called something like headcrabattack and can be found in the animations of a npc_citizen. Thanks guys.