One of the comments in that B-24 video Tony posted claims the impact/explosion was from AA, not a bomb from above. The more I watch that video the more I think that's correct. The stick of bombs that you can see in the video looks to actually be from the aircraft itself.
There was a longer piece of the same footage in a programme I saw; possibly World At War the Laurence Olivier UK prog from the 1970s. You saw the bomb in that actually hit. (Assuming it was the same footage)
I'm guessing, but I would have thought that if it was AA from below the plane would have been knocked upwards initially before falling, I'm also guessing that the blow out is vaporising fuel?
Regardless, God bless the poor souls in that wreck, they couldn't have had much of a chance.