As far as can be determined, Khabib Nurmagomedov leaped over the cage fence and scuffled with someone in the crowd, presumably Dillon Danis, McGregor's jujitsu coach. Almost immediately thereafter, parties from Nurmagoedov's team enter the cage and scuffled with McGregor and security, causing near-riot situations in Las Vegas. As to who threw the first punch, nobody really knows, however footage from the crowd does show McGregor atop the cage fence striking one of Nurmagomedov's team first in the scuffle - after which, two members of Nurmagomedov's team attacks McGregor from behind.
Following the fight, it's been reported that McGregor is unwilling to press assault charges against the people who attacked him in the melee after the match. Nurmagomedov apologised for his actions during a post-match press conference, where he had both belts at his seat and ending rumours that he may be stripped of his title. Currently, the Nevada Commission is withholding his fight purse pending investigation, whilst they have awarded McGregor's.
Here's what some of Twitter had to say about the fight and the aftermath.
— sphinx (@sphinnnnx) October 7, 2018
— Mike Tyson (@MikeTyson) October 7, 2018
— BossLogic (@Bosslogic) October 7, 2018
— lakhan (@lakhan809470) October 7, 2018
My main takeaway from tonight is that anyone that buys a ticket to a big event should have to take a class on how to shoot effective video on their phone. #UFC229
— pat muldowney (@patmuldowney) October 7, 2018