JACKSONVILLE, Fla. -

A photo taken by a Jacksonville Beach runner who had just completed his first Boston Marathon was described by the FBI as one of the best photos yet of the man the FBI called "suspect 2" walking away from the scene of Monday's bombings.

WJXT-TV reports David Green took the picture with his iPhone and posted it on Facebook earlier in the week. Thursday night, the FBI contacted him and asked him for the original, high-resolution version. The image was taken at the corner of Fairfield and Boylston streets showing several people running from the bombing. Suspect 2, wearing a white ball cap backwards, appears in profile walking away.

"And as I was walking, I saw bomb one," Green said. "The second bomb you heard and you felt from where I was. You were knocked back, and in that moment there was a lot of smoke and a tremendous amount of confusion and fear."

When Green ran back closer to the scene, he said he grabbed his phone to take a picture of the chaos. He said he did not remember noticing the man now identified as Dzhokhar Tsarnaev walking in the white hat.

"From there I ran to see if I could help people," Green said. "I was incapable of helping anybody because that was well beyond anything what I had seen or could deal with."

Green, who runs 100% Compression Wear, a sportswear company in Jacksonville, originally offered the photos to the FBI on Monday afternoon.  When he got home, he posted his photos on Facebook. The FBI contacted Green Thursday night asking to could get his original, high-resolution photo.

David Green's photo of suspect 2 close up (small) Green said agents told him that his picture was the best they had because it was taken from a better camera than the others that were posted.

Green is glad he was able to provide such a key piece of evidence to the FBI, but said he can't help but mainly be depressed when thinking about the day of the marathon.

"A lot of peoples lives have been hurt badly and anything we can do to help we should try to do so," Green said. "I plan to go run Boston next year."