Very nice sculpt so far. 
I do sense what you were saying earlier, that you usually work on Environments.
But in this kind of challenge, usually only the environment can help tell your story.
Just a few things I am thinking about:
“Explosive Liquid Filled Crystals” - This is like the ZX Poison in “The Rock”?
Maybe the case should be special looking… with “dangerous symbols” to help tell the viewer that there is real danger…
“La Souris” is a very small man(???) - I’m wondering how this will work.
The sculpting is great, of course for one of your skills. But I think you can also explore various “framing options”…
An interesting note on elevators. In most movies the Elevator contains the victim (eg: The Untouchables, Quantum of Solace, The Departed). Sometimes the cramped space gives Directors nice avenues to express “trapped” feelings and because the walls inside an Elevator are normally very clean… smattering it with blood or opening a set of Elevator doors to reveal a grotesque deed inside are good for audience shock/reaction.
So my opinion (only an opinion!) is that maybe the victim is inside the elevator… the bellhop has killed him, but sees the canisters falling… rolling… out of the elevator… towards him.
Then again, the entire scene can be inside the elevator…
Going back though to emphasize the bellhop… it may be interesting to note the Target had checked into the hotel and the Bellhop helping with his baggage killed him… So perhaps it is set right at the Target’s would-be hotel room door (imagine the vulnerability! Anyone can walk out of any number of the doors and see it if the Bellhop is unlucky!)…Or in his hotel room…
Lots of possibilities with this… but the prevailing thought would be to make the viewer grip his seat in suspense… 
Good luck!