It was flamethrower guy. He made the trap to get Wendingos so he could cage them up too. Think about it, it’s a human arm that’s constantly moving. The only two things that ever make a wendingo happy, movement and human flesh.

I think the inconsistency is the final part you play as Matt and he somehow knows to stay perfectly still to avoid the monster, yet he wasn’t around when everyone else learned about it because he was stuck in the mines, so how did he know that doing that would save him?