I have a tactical shotgun from my boat I use the same way on my truck camper. Same type of threads on boat forums by the way.
It's always loaded, no shell in the chamber and on safety.
It's where I sleep.
The big mistake in this story is leaving the door unlocked.
To defend yourself in either a boat or RV, when sleeping, you need noises to wake you up, as well as a single point of entry, hopefully a narrow hallway you're sleeping at the end of. Also a short barrel.
This way you are awake and ready if someone comes in and they have to file into a small area to get to you. Easy shot.
Key issue here was he had no warning since the door wasn't locked.
Even if you don't want guns around, escaping through an escape hatch is possible so long as you have that warnin sound of the door break in.