MMA fighter Joe Schilling -- who last fought professionally in 2019 for Bellator -- knocked out a man at a bar with a vicious combo of punches ... and the violent incident was all caught on video.
It's unclear when and where the barrage went down -- we're working on it -- but Schilling confirmed on his social media page Monday he was the puncher.
In his post, Schilling claimed he acted simply out of self defense ... writing he believed the whole situation was "life threatening" for him.