I believe the deceased Chinese woman is standing to the immediate left of 'bending over (guy, which could also be a woman [Tamerlan's wife?])'.. If it's you that has deshadowed the photo, great job. We could easily be looking at the pressure cooker, although removing it from a bag would be crazy BUT POSSIBLE, especially if a woman were doing it. It would be less suspect if a woman brought a pressure cooker, right?
Anyway, if the authorities aren't investigating this they must clearly have evidence which rules this out. Otherwise, game ON and it's compelling to see the detail of an otherwise hopeless photo.