According to Baltimore Sun
, last week Vince McMahon gave CM Punk the ultimatum of John Cena or Ryback as his opponent at Hell in a Cell.
When the time came for Punk to make a choice, he took too long and Vince McMahon said that he will make the choice for him later on in the night.
According to Bleacher report
, when the time finally came for McMahon to choose the opponent, Cena decided to step aside, saying that Ryback should be the one to go up against Punk at Hell in a Cell.
According to Wrestling News Source
, Cena started the "feed me more" chant and then Ryback stepped forward and signed the contract, making the upcoming match official.
Punk then decided to poke Ryback's chest, and that is when Ryback laid Punk out and then delivered his signature move, Shell Shock.