04/21/2013 AT 9:45 AM ET
Days before a Watertown citizen helped lead police to the second suspect in the Boston Marathon bombing, another ordinary civilian provided a photo that helped identify the most wanted man in America.
In the chaos immediately after the Boston Marathon blasts, David Green took a picture with his smartphone before helping those who had been injured in the second blast.
It wasn’t until three days later, when officials released video of the two suspects, that Green realized that he had a clear photo of suspect Dzhokhar Tsarnaev walking away from the scene.
Green, the CEO of a sportswear company who ran the marathon, immediately understood the importance of taking the picture. “I was in New York during 9/11,” he tells PEOPLE. “You just have to document something, [so] I pulled my phone out and took one picture.”
“Then I ran into the crowd to help whoever was there. I got back to the hotel, called the FBI and said I had the photo, then I posted it on Facebook.”