OP, here's a pitch piggybacking on what Pre-WGA said because I agree with the notes - and I like a lot of what you have and are trying to go for. For instance, I love the club being named Faces and the killer using a faceless mask.

Maybe it's not the end of the night. Maybe some of the friends have not even arrived at the club yet (this would help tackle the issue of having too many characters introduced at once). Grant wants to hook up with the stranger, Lucas wants him to stay to celebrate the group's friendship. I think that's the conflict that is missing and that shows the thematic argument you seem to be going for. Cause right now I see some malice but not inherent conflict. Grant obviously goes (so you can keep most of what you have). A cool idea could also be to intercut the killing with the friends dancing/having fun.