Dave Meltzer is reporting that an altercation between Chris Jericho and Brock Lesnar went down backstage following the conclusion of SummerSlam, with the two getting physical after Jericho deemed that Lesnar was too reckless in the handling of the closing of the match.
Jericho rushed to the Gorilla position to see what exactly was planned and when no answer was given to him and Lesnar walked in, all hell broke loose. Lesnar did not appreciate Jericho getting involved in his business and a war of words ensued, with the two putting their hands on each other and ending up against a wall.
Triple H and others, including Vince McMahon, broke the fight up and McMahon, according to Meltzer, informed Jericho that the ending went according to plan. Orton, who came in afterward, told Jericho that he knew what was coming.
While Jericho is usually a total professional, watching one of his friends get manhandled like that with not much safety to his health was a bit too much for him. Meltzer also adds that it was Brock Lesnar who first misunderstood what Jericho was saying backstage as he walked in and he was the one who started the fight.