As Americans watched the horrific events unfold at Monday’s (April 15) Boston Marathon, celebrities took to Twitter to express their thoughts.

The annual race, which draws runners from all over the world, was held in memory of the teachers and students who passed away in December at Sandy Hook Elementary School.

New Kids on the Block member Joey McIntyre was in the race, and had just crossed the finish line about five minutes before the two explosions rocked the area.

President Obama addressed the nation Monday evening, calling the bombing an act of terror and promising to bring the perpetrators to full justice.

Check out what celebrities are saying about the event below.

Lindsay Lohan: “Sending prayers to everyone who was/is at the #bostonmarathon”
Pink: “Our thoughts and prayers are with everyone affected by the explosions in Boston.”
Ashley Benson: “Praying for loved one in Boston so horrible.”
Gisele Bundchen : “My thoughts and prayers to everyone in Boston #prayforboston”
Khloe Kardashian : “So many unspeakable tragedies! My heart, love and prayers go out to anyone affected by the sad events in Boston. #PrayForBoston”
Olivia Wilde: “Oh for f*cks sake. I’m so disturbed by the reports from Boston. This is horrible.”
Justin Timberlake : “My thoughts and prayers are with everyone in the city of Boston and all of those affected by this terrible incident.”
Channing Tatum: “#prayforboston”
Ben Affleck: “Such a senseless and tragic day. My family and I send our love to our beloved and resilient Boston.”
John Krasinski: “My heart and my prayers are in Boston and with everyone affected by this nightmare of an incident.”
Kim Kardashian : “My heart is breaking for everyone affected or injured in the explosion at the Boston Marathon. God bless you all! My prayers are with you!”