Let him go. Get as much visual info you can and call the police. If he turns to run, your life is no longer threatened. As stated before, check your local laws. Here in the firearm freindly state of Massachusetts
, I believe you could be the one in trouble drawing at that point. I am admittedly not expertly versed in our often confusing laws here, but if you or a loved one is not going to die, don't draw.