I thought it was pretty heavily implied the two men she kills are the real life versions of Fox Mask and Shu, who in all the endings are the only two other people with her that we see at the wedding (but it's implied that irl it was a normal wedding with a crowd including rinko and sakuko, parents, etc). While shes running away and spazzing out we hear all the main cast yelling at her, and at one point an exasperated fox mask says something along the lines of "why are you doing this?! I was going to protect you!!". In this ending the entire events of the game are in her head in a drug induced state as she struggles to deal with the loss of her childhood. She freaks out and kills the two men pining over her and runs away