Couple of things I find interesting HL, these people were smoking pot (how did you know it was pot? Did you get that close?), and peeing in a park... I assume these people were peeing in a wooded part of the park and not down the slide or something like that (I know I have given you the perfect answer to this to lie to me, but I think you'll tell the truth). What's wrong with that? Do not animals per in the park everyday? In sure birds drop loads or uric acid all over the swingset, yet you don't mind them... And marijuana.... Why do you care they were smoking marijuana? Was it harming you, or affecting you negatively in a way a cigarette smoker would not?
Then, you go and resort to violence. Did you ask them politely first to leave because for some reason you felt uncomfortable with them smoking in your park? I doubt it. (again, go ahead and lie here if you want, too)
You seem like your resorting to violence is symptomatic of some mental disorder. If I were to pee in the woods in a park, and someone shot me with a paintball gun, you better believed I would have retaliated, and I'm a crazy pot-smoking-park-pee-er too (in this hypothetical)! I might just eat your face off!
Dude, you gotta calm down. I literally cannot believe you shot someone, go seek medical help immediately before you see a real crime and decide to shoot them with a real gun next time: "Man Massacres group of Teenagers Vandalizing Park."