What would you do as a citizen

the explanation must include the following:
What would you do as a citizen if you were legally carrying a firearm?
Would you act differently if you were a responding police officer?
Do you have the right to use deadly force?
What factors are the most important in your decision to act or not to act?
Most importantly, be able to articulate why you did what you did (shoot or don’t shoot).
Scenario:
You pull up to a gas station to get gas and see a man pointing a gun at another man on the ground. The man with the gun is yelling at the man on the ground and almost seems incoherent. He is shaking his gun at the man on the ground, but not waving it at anyone else. All of the man’s anger seems to be directed toward the man on the ground. There are people running away from the scene pointing and yelling “Help him!” you have no idea what’s going on, but what do you do? Based on this limited set of circumstances, what are your choices and what would you do as an armed citizen, then if you were a first responding police officer?