'Jackass' Star Is Hacking Victim After Death

Ryan Dunn from "Jackass" is tweeting bizarre messages -- which is weird due to him being dead -- and his family's on a mission to stop the "disgusting" hackers, stat.

The tweets started posting a few days ago and were written as if it were Ryan from beyond the grave. One of them joked Ryan had met Harambe the gorilla in heaven -- and another references Tupac.

Ryan's mom, Linda, tells us the posts aren't coming from any friends or family ... and she has no idea how the account got hacked. They never took it down after his death.

You'll recall, Dunn died in a 2011 car crash -- he plowed his Porsche into woods at 130 MPH following a night of heavy drinking.

Linda's reached out to Twitter to have the hacked tweets removed, but so far she hasn't heard back.