Lou Taylor Pucci victim of random attack

Pucci's father tells TMZ the actor -- who's had roles in movies like "Fast Food Nation," "Fanboys" and "Brotherhood" [and "Thumbsucker"] -- was the victim of a random act of violence on July 3 outside of his friend's house in Belmar, NJ.

We're told four unknown men were walking past Pucci when one of them suddenly attacked him -- knocking him out cold and breaking five bones in his face.

We're told the mystery assailant took off on foot and was never captured -- and Pucci has since had a titanium plate put in his face.