Sure. I'll play. I assume those sensors are always powered and never malfunction and so, now the train is stopped in a vacuum. What now? How do we get the people out, and all the trains behind them now also stopping. If the tracks are below ground, where is the nearest valve that can open? Given some parameters to chatgpt, because I can't be bothered to do the math myself, it takes ~5 minutes to fill a 500m section with air. So, that assumes a 500m sealable section with an independent valve. So, there would need to be some kind of system that can seal a section on power loss or breach, without a train running into in-progess.... so, 500m sections are too small. The sections need to be ~5km which would take nearly an hour to fill with air that won't kill you instantly. So, if there were structural integrity issues with the train, everyone is guaranteed to die. If there is a critical power loss, hope that it can scrub the CO2 out of the air for at least an hour without power. If there is a breach, hope that it isn't in your section or is at least 3 sections away.
Killing everyone in the train because someone gets in a fight and fires a gun is pretty much a non-starter. That's the real problem you got to solve. It's not like a plane where someone can fire a gun in nearly any direction without consequence to the plane, firing a gun in literally any direction on a hyperloop would mean certain death for everyone on board.
It's in a vacuum, it's not like you can drop oxygen masks. In a vacuum, your blood boils and your eyeballs are sucked out. It's a pretty shitty way to go, but you'll lose consciousness before the worst of it.
