For those who have not seen, a masked man appeared at the end of the show to help Ace Steele defeat Daryck St Holmes. The masked man, sporting a hoodie that Punk had worn earlier in the day at a BJJ tournament, entered the ring while the referee was down and hit DSH with Punk's GTS finisher. The masked man then darted out the door and was not seen again.
Wrestling Inc. has learned that at one point the plan had been for Punk to actually take the mask off after hitting the GTS. That did not happen, obviously, and Punk left while masked after the match. We have also been told that Punk waited in his car outside the venue before making his appearance and left immediately afterwards.
You can see the side by side comparisons of the masked man, and CM Punk, earlier in the day in the embedded tweet below:
Here is the picture comparison for CM Punk and the masked person. This would really be something. I do not know who made this picture, so I do apologize for not being able to attribute, had it sent to me. pic.twitter.com/NtS2XC5HbU— Jon Alba (@JonAlba) April 21, 2019
Here is footage that MKE Wrestling has shared from the event of the run-in: