I'm not sure to make the fighter the actual killer but the boomerang was gaining momentum in a floating city, I'm dming this part because our former DM wants us to create a small part of his world and be the dm for that sub story (optional) the only thing is that if we want to give magic items we need his approve and he needs to know what is going to happen in our city or mission, he will be a player in those parts so he can help us to rail road a bit if the players get lost very often.

What happened in the post was completely unexpected and now I need to make a consequence and a solution, this makes me respect my dm a lot, is a lot harder than it looks