Well, since Wild Alaska has gone silent, I'll explain civil lawsuits.
First, a plaintiff must be harmed. In the case where a home invader with a gun is shot, he could allege being harmed. However, if he's dead his estate must filed the suit for him.
Second, a person must hire an attorney. Attorney's value $. Not the promise of money, but REAL HARD cash money, and lots of it. A civil suit of this nature would likely cost the plaintiff tens of thousands of dollars. BG's that are robbing you and their families are probably in short supply. Another option is a contingency fee, which means that the Attorney will work for some portion of the final settlement/judgement, generally about 1/3rd, PLUS the costs (which will amount to a large chunk of money, which again the BG doesn't have).
An attorney working for cash MIGHT take a loser case just for the $, but probably will not because attorney's like to win. An attorney will NEVER take a loser case on a contingency basis because he won't be paid for his years of work. Simple fact.
Now, given that his client was in my home uninvited or illegally, with a gun, wearing a ski mask, with clear intent to do harm and rob, and was shot (maybe killed) in the process, that's not a very good case. ON TOP OF THAT, Colorado statutes provide for complete immunity from civil liability in such defensive shootings and it doesn't matter if it was in the back or if I tickled him to death. Homeowners have the absolute right to use lethal force to confront lethal force.
Now, presented with these facts AND the immunity statute, NO LAWYER IN THE WORLD is going to take this loser of a case because the judge will read the complaint and then the answer and toss it out.