The last option lmaooo
I do agree though, he is suspicious, but I also can't help but suspect if he's just a red herring. I also think that one Dullahan is a bit sus, the old man that has appeared so many times - haven't his incidents coincided p well with some of the big mystery, if I remember right?
There's not that many side characters who aren't around MC a lot of the time (ie. colleague) or who appear without MC having something to do with it/related to them (ie. familiarity with the kids, already has contact to the reported, a familiar police officer). Like.. he's just appeared, more than once, and rn I can't really remember this being pointed out or mentioned in the story to clear it (ie. exchanging contacts or establishing some other more natural relationship besides "oh noo i need help and you're conveniently here"
Haven't reread this story even once so I might be misremembering, do feel free to correct me if you remember better than I do!

Bearhead boss is so suspicious. Either he's the main villain or someone from MC's past (or the love interest lolllll)