There is absolutely no chance of it ever being murder in the first degree. A district attorney would know not to charge that because it would just get thrown out by the judge. A gun should be your last line of defense. Since you weren’t defending yourself, pulling it out is enough to get a criminal charge. I know you didn’t know this at the time and had no way of thinking about it while in the moment, but at least now you know for future reference. What will suck even more is paying the court/lawyer fees afterwards.