When I was with American Rifleman we got one in to test fire.
I was standing with the tech who was test firing the gun with shells loaded with No. 6 shot.
The nailer for the targets was a 2x4 at the top edge of the trap. At 15 feet, the pattern thrown was so wide that many of the shot hit the 2x4 nailer.
Even worse, though, was that because of the short barrel, the No. 6 shot didn't get enough velocity to penetrate the soft pine 2x4, and they rebounded back at us.
I was hit with at least 4 pellets that rebounded -- in the neck, right ear, cheek, and 1 in the shooting glasses I had on, dead center with my right eye.
The tester was also struck with several pieces of rebounding shot.
In a room, where there are a lot more surfaces from which the shot can rebound, I can only imagine that it would be a LOT worse.
Quite frankly, the Thunder 5 IS silly.
Shot loads are pretty much worthless out of it.
The 3-ball buckshot loads showed horrible accuracy at 15 feet with patterns of 20" or more.
The .45 Colt bullets also showed pretty hideous accuracy, but at least would be marginally passable.
If I were broken down in a bad neighborhood, I'd want my Beretta or one of my Smith .357s.
If you need a gun, get a gun. If you want a toy, there are toys out there that are a lot cheaper.