Customized M16A1 Assualt Rifle

The third assassin who shoots up Frank Martin's house uses a M16A1. It appears to be a standard M16A1 with an unusual A2-ish forearm and a strange upper section that looks like it's trying to copy a Beretta AR-70/90 in general shape and style (especially the forward slant of the carry handle), it's possible this might be a very old school laser aiming device.