Okay, looking at this picture one more time, it does appear to have been photoshopped.
Furthermore, the caption on this image seems to indicate that the photoshopped job has an agenda.
Note: One can find lots of these photoshopped images all over the Internet as sick jokes.
It is disgustingly sick to make fun of acts of terrorism whoever perpetrated them. People have died.
Nevertheless, this image might not have been photoshopped as it was published by the Boston Globe by one of their news photographers. Below is a plausible explanation.
There could have been two groups: (1) a group of policemen standing outside with the plainclothed officer looking up to the roof, where the lid of the pressure cooker bomb might have been found; and (2) a second group of officers inside that office building with the blown out glass. Notice that without the glass, there would have been no reflection. Indeed, the appearance of a reflection does not match the officers standing outside. Also look carefully where the officers outside are standing: most are standing near the alley way, where they would not have been captured in a reflection.
If this indeed were an undoctored picture, it would certainly be a masterpiece.