After two explosions detonated at the finish line of the Boston Marathon halfway through the race, social media has been filled with reaction from horrified witnesses and celebrities.

New Kids on the Block star, Joey McIntyre, Tweeted that he had just finished the race minutes before the bombs went off. Before starting the race Joey had Tweeted a photo of himself, stating he was running to raise money for both Alzheimer’s research and the Massachusetts Eye and Ear team.

Three people were killed, including an 8-year-old boy and more than 170 people were injured following the explosions.

Matt Damon released the following statement to ET Canada: “My heart goes out to the people of the city of Boston. My thoughts and prayers are with the families who lost loved ones in such a senseless and heartless way.”

See the celebrity reaction on Twitter below: