Brad Pitt Attacker Vitalii Sediuk -- Ignore My Maracas ... Community Service Is No Joke!

The guy who's doing time for attacking Brad Pitt claims to be taking his sentence very seriously -- despite the fact he was spotted shaking maracas in the middle of his punishment.

We spotted Vitalii Sediuk leaving an L.A. grocery store and asked him about the video (below) of him joining a drum circle the other day ... while he was supposed to be doing his 20 hours of community service for the the red carpet incident.

Believe it or not ... Vitalii has an explanation that makes sense, and assures us he's serious about the "experience" of picking up trash and cleaning public toilets.

As for Brad Pitt's face being on his chest -- there's no good excuse for that.