I'm looking for the title of a short story I read years ago.
It is about a cop chasing down a serial killer but it turns out both of them are actually aliens and the cop turns into a blob and envelopes the other alien until it dies.
It was part of an anthology. I read it maybe 7 years ago but the anthology could have been much older than that. For some reason I keep thinking it was in a horror anthology as opposed to to a straight up sci-fi anthology. The story takes place on Earth and it reads like a standard cop/detective story but then you get to the end and boom you get the alien twist.