According to TMZ
, the incident took place when Punk ran into the crowd after a match. Several fans were then getting physical with him.
Punk shrugged off the fans at first, but he got mad when someone made contact right to the back of his head.
According to Examiner
, the fan that was punched by Punk said that he planned on filing a police report, and he said that he never hit Punk.
According to Bleacher Report
, CM Punk apologized for the incident, and the WWE said that they regret that proper security measures were not in place.
In the video, Punk can be seen being hit in the back of his head, but when Punk turned around he ended up punching a fan who did not hit him.