The only picture I have seen so far, where the person does have on a light hoodie, black jacket and white hat worn backwards it this one.
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It was linked early yesterday by another poster, but seemed to get completely ignored.
From reading that the video shows the POI dropping the bag at the second site while on the phone while the first bomb detonated, I'd be inclined to believe that this guy is not the right person either, since he was on the other side of the street. I don't know how easy it was to cross the street while the marathon was on.