IT WAS NOT AN OXYGEN BOTTLE EXPLOSION.
2 ways an oxygen bottle explodes:-
1. The head fitting (regulator) blows off. In this incident the bottle would take-off like a rocket, and because its orientation onboard the aircraft was in a vertical position then it would have left a big hole in the bottom of the fuselage. And yes they are adequately secured and have over-pressure relief valves and check valves and thermal relief and every other protection device you could think off . So this did not happen.
2. A breach in the wall of the cylinder, very unlikely but lets say for the argument this did happen. This would be equivalent in force to an explosion as large a bomb going off, and depending on the direction of the blast possible shrapnel damage. If blast direction was inside then expect to see the cabin floor being lifted. If the blast direction was outboard then expect to see more damage and not radiating from a small point in the middle of the hole in fuselage.
Oxygen bottles just don't explode like this, if it was contamination from galley waste that triggered the explosion combining with small leak from cylinder then again the regulator is where that would have occurred.
Yes there is at least one bottle missing but only because the structure supporting it has disappeared.
THINK AGAIN.