It was sudden and abrupt during a New York City when New Kids on the Block member Jonathan Knight just up and left stage, and didn't come back. 

When you go to a NKOTB show, you expect that all of them will be there. For most of the show on Thursday night, they were. Except for when suddenly Jonathan Knight just left. He didn't come back either. In the video below, you can see when things start to get weird.

According to Yahoo, Knight has long been dealing with anxiety and panic attacks. Obviously this must have been a case of this. The crowd and his band showed him major support. On Friday NKOTB posted on twitter that Jon was doing just fine, and were on their way the Napa, CA.