I don't know what they are. But I saw some when I was very depressed. I saw them twice which is more than enough. A friend who knows more about them told me if you see them more than twice its really not good.
I know there are sereval types of them. The most dangerous ones are the hat men.

I am also thinking I may have just been stressed out/delusional but many people saw these creatures before. I haven't seen any for years though.