(Photo credit: @joeymcintyre/Twitter)

"New Kids on the Block" singer Joey McIntyre competed in the Boston Marathon today to raise money for the Alzheimer's Association (his mother has the disease), but as was the case for so many runners, what began as an exciting day took a horrifying turn just moments after he finished the race.

"There was an explosion by the finish line about 5 minutes after I finished," McIntyre, 40, tweeted earlier this afternoon. "I'm OK but I'm sure there are many hurt."

ABC News has confirmed that two people have died and at least 86 were injured in a series of two blasts that exploded near the finish line of the race. Police then said that a third explosion occurred later at John F. Kennedy Library, but no one was injured.

"I'm OK. Most importantly, praying for those injured and affected by this," tweeted "Survivor" winner Ethan Zohn, who also ran in today's race. "Still don't have a lot of info. Thanks for your love and concern."