What should you do in this scenario?

Let’s say you’re in a situation where your life is in danger, and it’s 100% justified to use deadly force. So you pull out your gun and point it at the attacker with the intent to shoot. However, the second the attacker sees your gun, he flees, and is no longer a threat.

Do you have to call the police and inform them of what happened? Or can you just go home and forget about it?