From the spoilers I've read
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Its him. If I'm not wrong, he also tried to find the cause why they always die together on that same room and same day but he couldn't find it too. He just knew they would repeat dying and that he could not help but just wait and find them dead there. Imagine being helpless each timeline and you cant prevent their deaths. Dw, miguel is still our good boy

Miguel pookie tell me if you did it if you admit the truth now I'll let you off with one stab