Jonathan Knight Walks Offstage Halfway Through New Kids on The Block Concert [VIDEO]: Singer's Anxiety to Blame? Joey McIntyre, Donnie Wahlberg Joke about Sudden Disappearance

During a New Kids on the Block live-streaming concert event in NYC hosted by iHeartRadio on Thursday (April 4), singer Jonathan Knight suddenly up and walked offstage halfway through the performance - he remained MIA for the rest of the evening. Following the show, Knight (who's been very open with fans about his ongoing bouts with anxiety), tweeted the simple message, "I'm sorry..." Fellow band mates Joey McIntyre and Donnie Wahlberg tried to make light of the situation, and finished off the set without any more problems.

According to inside sources, Knight's odd/anxious behavior began earlier on in the performance - he remained out-of-sync with his NKOTB band mates, and kept playing towards the back of the stage. At one point he even took a phone call on his cell in the middle of the set. Finally, he walked offstage mid-song, and would not return despite fans in the crowd chanting his name.

Prior to the show, Knight tweeted:

@JonathanRKnight: "#ifeelnaked."

Following his disappearance, the singer tweeted:

@JonathanRKnight: "I'm sorry......"

Knight has remained very open with fans about his ongoing history with severe anxiety and panic attacks - it remains unknown if that's what caused his sudden stage walk-off on Thursday.

Following Knight's mysterious disappearance, fellow NKOTB members downplayed the seriousness of the situation, joking that Knight was stuck in the bathroom and that the absence would definitely "make TMZ."

"We love Jonathan and he loves us," McIntyre told the crowd.

After the show Wahlberg amusingly tweeted:

@DonnieWahlberg: "To recap- Joe was especially dazzling! Jordan was especially amazing! Danny was especially solid & Jon was especially shy! #Allsystemsnormal."

Here's to hoping that everything's ok!

NKOTB is expected to kick off the Package tour (also featuring 98 Degrees and Boyz II Men) on May 18, check out the full tour-date lineup below:

May 31 Uncasville, CT Mohegan Sun Arena
June 1 Uniondale, NY Nassau Coliseum
June 2 Boston, MA TD Garden
June 4 Ottawa, ON Scotiabank Place
June 6 Montreal, QC Bell Centre
June 7 Toronto, ON Air Canada Centre
June 8 Auburn Hills, MI The Palace of Auburn Hills
June 9 Cleveland, OH Quicken Loans Arena
June 11 Pittsburgh, PA Consol Energy Center
June 13 East Rutherford, NJ Izod Center
June 14 Washington DC Verizon Center
June 15 Philadelphia, PA Wells Fargo Center
June 18 Nashville, TN Bridgestone Arena
June 19 Charlotte, NC Time Warner Cable Arena
June 20 Atlanta, GA Philips Arena
June 21 Orlando, FL Amway Center
June 22 Fort Lauderdale, FL BB&T Center
June 25 Cincinnati, OH US Bank Arena
June 27 Houston, TX Toyota Center
June 28 Dallas, TX American Airlines Center
June 29 Oklahoma City, OK Chesapeake Energy
June 30 St. Louis, MO Scottrade Center
July 5 Los Angeles, CA STAPLES Center Arena
July 6 Las Vegas, NV Mandalay Bay Events Center
July 7 San Jose, CA HP Pavilion
July 9 Tacoma, WA Tacoma Dome
July 12 Rosemont, IL Allstate Arena
July 13 Minneapolis, MN Target Center