Billy's scream is not a scream of pain. It is actually a scream of fear. The reason it is a scream of fear because the Predator appears. Most people assume Billy is murdered on the bridge. Billy is the last member of the team to die. (Anna is not a official member,guys). Billy manages to start to combat the Predator. Though, the alien leaves to kill Poncho, injure and chase Dutch. Though, it is unknown if the Predator wounded Billy or just left. I believe the creature left, knowing that Billy would be more difficult to handle, unlike Dillon. The alien likely to leave, knowing performing a ambush on Dutch and Poncho, not on Anna, just saying. Once the Predator disappeared, after its chase on Dutch,it returned to fight Billy. It was likely to be a good fight. Billy and the Predator are strong. However, Billy has never fought a alien life form. Dutch does not combat the Jungle Hunter, as he defeats with traps, not himself. Billy only had a machete. He is not victorious, as he is the final victim of the Jungle Hunter. Once again, the scream that came from Billy is not of pain, it is only of fear. After the two fight on he bridge over the ravine, the Predator manages to wound Billy, to the point where he could not start fighting the alien. The Predator removes Billy's spine and lets it drop in the trees below. Billy was a worthy opponent, but sadly, he was not able to stop the Predator.