After leaving a village, Gibson and his friend Nady are attacked by pirates or whoever. They run into a large concrete building where most of the fighting takes place. Gibson uses a toe spike on his boot to cut someone's throat. Right after that he's attacked by a big guy with two knives. Gibson breaks this guys arm, then it seems like he stabs him in the back. This is where you have to use slow motion. You can see (from two different angles) that Gibson drops the knife as he pretends to stab him. In the first angle you can see a clearly open hand with the knife resting in it. In the next angle you can also see an open hand, plus the knife falling at a weird angle.