You are 100% wrong. Buying weed in the streets is illegal. They even tell you at the dispensary that resale of their shit under any circumstance is illegal.
When you ask a person in the streets for weed, you are doing criminal shit. Yes. You were doing criminal shit. You asked a criminal for weed.. then returned it. That's bad street etiquette.. him brandishing a gun in this situation is perfectly acceptable for the shit you were doing and the way you were acting.
Your HORRIBLE decision making skills led you to that very natural consequence.. THEN instead of realizing you were wrong, and should just leave... You proceeded to call the police about a situation you created. That man was minding his business until you showed up.
You have no idea how lucky you are to still be alive. And you should really stay in the house. You don't have the awareness or comprehension skills to be allowed to roam freely. There's so many ways that shit could have went left.