Nicknamed "The Predator", Groenhart lived up to his name by knocking Grogian out from behind but quickly turned victim as fans stormed the ring to attack the Dutch-born fighter.
After the win, the kickboxer explained he had done nothing wrong with his knockout, because the referee did not step in to stop the action.
Five years later, the second fight was entirely different from the first with Groenhart getting the best of Grigorian from the sound of the opening bell.
The punch appeared to legal and the ref did nothing to signal the round was over or time was taken out.
One fan landed a flush punch to the kickboxer's face, who said after the melee that he may have suffered a broken jaw.
"Grigorian's trainer Nicky Hemmers said on the broadcast that his fighter turned his back due to a cut - "which you never do in a fight", he said - and he didn't hold it against Groenhart for hitting him". "I got my guard up". I think it's broken [jaw], I don't know.
Grigorian made the catastrophic error of turning his back on his opponent and was punished with a destructive right hook - sending him crashing to the canvas. The referee did not come in.
One of the craziest things I've ever seen at a fight. "I was like come on guys this is a sport". I did nothing wrong.