I think running would be a good idea so long as the gun is not pointed in my direction. In fact, I would run if I think I have more chance of getting out of there alive. But in open space, chances are I won't. In which case, I will proceed to attacking the person straight away, no question asked. It's all about charging while minimizing exposing of your vital organs. If I somehow made it to the guy, I will either try poke out the assailant's eyes, an elbow to the neck or jaw (good for stunning), or kneeing the crotch if it's a guy. Hopefully adrenaline will keep me going even if I got shot along the way. Once the person is down, then it's a matter of curb-stomping the guy, possibly in the wrist, knees, or head to make sure he stays down (or dead).
Yes, to death. I love my life. If anyone threaten my life, then I will have absolutely no reservation about putting out theirs.