unknown person on facebook?

[Miranda]

Hello there's this person who I don't know suddenly keeps on appearing on the news feed posting dirty images. I don't remember befriending that person and when I try to click to his profile, it says there that the page does not exist. Until now it stays that way and I cannot delete him from my friends. and On the pictures he posts, there are many comments of people saying like 'who the hell are you'. What is that actually? Is my facebook being hacked? o.O and how can I get rid of it