New Kids on the Block singer Jonathan Knight walked of stage during a concert at New York City’s iHeartRadio Theater Thursday, according to the New York Daily News. Though he failed to offer an explanation for his early departure, Knight took to Twitter to apologize to his fans. “I’m sorry……” he tweeted.

The Daily News reports that Knight’s fellow band members tried to ease the tension by suggesting that the singer needed to make a quick pit stop to the bathroom. “We love Jonathan and he loves us,” Joey McIntyre reportedly told the crowd.

It’s not clear at this point if Knight’s exit was temporary or permanent. Regardless, NKOTB has a busy schedule in the coming months, as the band prepares to tour with Boyz II Men and 98 Degrees.

This isn’t the first time nor will it be the last that a singer has walked off the stage before a concert has ended. According to TMZ, Kings of Leon lead singer Caleb Followill left the stage during a concert in Dallas, Texas, in 2011, because he needed to “vomit.” Followill never returned to finish the show.

Justin Bieber, on the other hand, doesn’t show fans the courtesy of walking off stage when he’s sick and actually vomited on stage during a concert in Glendale, Arizona, last year. According to USA Today, Bieber wanted to give fans the best show ever.

What caused the veteran concert singer to walk off the stage? Did the NKOTB singer have stage fright or was he suffering from some sort of ailment? Have you ever been at a concert where one of the performers did something unexpected? Share your thoughts and experiences in the comments season.

Whatever the reason for his early exit, Knight or one of the other members of NKOTB is likely to offer a plausible explanation for the incident in the near future.