New Kids on the Block had just released their new album "10" on Tuesday and yesterday were performing a iHeartRadio event that live-streamed on Yahoo! Music.  Everything as going well until singer Jonathan Knight walked off stage. 

If you start the video at about 26:00 minutes, the guys are starting singing but Jon never comes in with his part.  It is unclear if Jonathan truly forgets the words to his part of the song or if he is just too emotional to sing as his band mates joke with the audience to calm the tension.  Donnie Walberg tries to lighten the mood by saying, "Jon, these people paid thousands of dollars for these tickets and for one reason, they heard that you are singing on this record."  You can hear the fans in the crowd trying to make Jon feel comfortable shouting, "I love You Jon!" but nothing seemed to work.  His brother Jordan tried to sing the first few words of his part, but Jon never picked up.  After a few more seconds, Jon slipped back and off the stage while his brother Jordan starts singing his part.  

The guys mention several times that Jon will be back, however Jon never comes back on stage for the rest of the show.  

Jon tweeted after the show simply, "I'm sorry...."

Jon has been dealing with panic attacks and anxiety issues for several years.  In a revealing tweet even before the show happened that day, Jon twittered, "#ifeelnaked".  

New Kids On The Block twittered saying"Not 2 worry BHs, all is well w Jon!" also "It was crazy album release week & we are all on a plane to Napa & look fwd to a grt show this weekend!"