If I block someone after sending a message on facebook, will it still show my name?

So I found someone on facebook, that I am not currently friends with on facebook, but didn't want to add them, but wanted to message them on facebook for closure and to close up some bad history from the past, well I know theres no stopping the message, and they are going to be able to read the message regardless, but I kinda wish I didnt even bother contacting them. Anyway, now I would like to block them, but I was wondering when I block them, I know they will still get the message, but will they be able to know that its from me? Like will my name still show up? or will it just say "facebook user"? and be blank?