Nate Diaz delivered the "Stockton Slap" to a member of the media backstage at UFC 276.
"OG" Shawny Mack of Full Send MMA approached Diaz and asked if he was there to see Sean O'Malley compete on the card. The UFC star admonished Mack for some recent posts on social media before knocking the microphone away and slapping him.
The origin of the beef is unclear. Per Jason Hartley of MMA On Point, Diaz may have taken issue with something Mack said about Nick Maximov, who has trained with Diaz.
It doesn't appear things escalated beyond the slap that was captured on video.