I have slo-moed through than scene many times & honestly, the object was fired at him, not tossed. Which pretty much rules out the throwing chunks of flesh or blood at him. My guess is that it was from a weapon which wasn't revealed in the movie. It wasn't a caster shot, because you can hear the trademark "crack" of the caster firing a mile away, my guess is that it may have been a round from the speargun fired as a warning shot