Even if their goal was purely to steal something, things progress very quickly in chaotic situations like those; especially when their state of mind could be affected by drugs or mental illness. And you have no idea what their goals actually were or are.
Milliseconds matter, so there isn't really a better way to handle that situation, in my opinion. It'd be nice if there existed non-lethal weapons which could incapacitate as effectively as lethal ones, but they don't seem to exist yet.
If it were a death sentence, then you'd be allowed to shoot someone in the back after they've exited the house and are running away. And obviously you aren't; that'd be murder.