regardless of the law, you did the right thing.
first off, i speak as someone who's never been in a similar situation, so those of you who don't agree with me are welcome to disregard my .02. i have been in situations where i had to take action against someone who meant me harm though, and in those situations it's a lose/lose situation, psychologically. whether you act or not you end up regretting that your choice, and second guess yourself as to what was the appropriate course of action. i do, anyway.
2 things to consider:
1) to shoot because you were afraid of some future break-in would have been acting out of fear. by not shooting, what you did was the brave thing.
2) the ability to use force is power, no one would argue that. but the power comes from having that potential - not from acting it out. once you have acted to harm another, that power is gone. in this case you would have transferred power, as the potential threat of action, out of your hands and into the hands of the legal system - and thus possibly into the hands of the bg.
remember the meaning of "si vis pacem, para bellum" - if you want peace, prepare for war. being prepared is in order to ensure the peace, not ensure the use of force. it's the threat of the ability to employ force that gives one power. not its execution.