"Everybody knows somebody who was directly impacted by the bombings at the marathon, and what a horrible tragedy it was," he said over the weekend after he surprised runners ahead of Monday's marathon. "When they decided they were going to make this movie, they had come to me and asked if I wanted to be a part of it, and I was like, I don't think it's a good idea."
In seeing the screenplay about that tragic day that left three dead and over 250 injured, his mind was changed.
"But then when I read the script then I realized, oh my God, this is so powerful and so inspiring and such a tribute to everybody: victims, the rescue workers, the police department, the FBI, everybody," he said.
"I also realized that if I wasn't going to be a part of this somebody else was going to be," he said, "and I didn't know if they would handle it and be as committed to getting it right as I would. So, I figured, you know what, I needed to be a part of this and I am so glad that I did."
On April 18, thousands again took to the streets of Boston for the 120th running of the Boston Marathon, which also marks Patriot's Day, an annual local holiday that features both the marathon and an 11 am start time to a Red Sox game (games typically begin at 7:05 pm.)
It's a big day for the area, as celebrities and athletes often run the marathon. In 2014, New Kids On The Block star Joey Mcintyre ran the 26.2 mile course. On Monday, Jake Gyllenhaal threw out the first pitch at the early baseball game along with Jeff Bauman, the man Jake will play in the 2017 film "Stronger."
The significance of the day isn't lost on anybody in the area. On Monday, Tom Brady took to Facebook to share a photo with a bombing victim.
"Two years ago I was lucky enough to meet Adrianne Haslet, a survivor of the 2013 Marathon bombings," he wrote. "She's on the course now, running the race for the first time -- with a prosthetic leg. Adrianne thank you for being my inspiration!! #BostonStrong."