Bingo. When you have violent thugs chasing you before trying to take your gun, what other option do you have? Hope the extremely disturbed individual doesn't shoot you after taking your gun? You can't be expected to put your life in the hands of a deranged person that has already threatened to kill you.

And as for the second encounter, if you're not within your rights to shoot someone when they have a gun pointed at your head, you'll never be.