Unclear if words were exchanged between them, but after Conor downed a shot with the other drinkers, he unexpectedly threw his notorious left fist and decked the old man who rejected the shot.
Two people immediately grabbed McGregor and pulled him out of the bar. The violence was reported to cops, who announced back in April they'd opened an investigation. It's unclear if that's still active, but there are no reports Conor was ever charged even though cops have reportedly seen this video.
Perhaps most odd of all the poor, old pub patron who got socked didn't even get knocked off his stool. People are just tougher in Ireland, apparently.
The video is just the latest evidence of McGregor losing his cool outside the Octagon. He dodged felony charges in New York last year when he smashed a bus window with a dolly, injuring several UFC fighters onboard the vehicle.
One month before this Dublin incident, Conor smashed a phone out of a fan's hand in Miami. He was arrested for robbery and criminal mischief, but the charges were eventually dropped, and he settled a civil suit with the victim.