He should have called the police, not doing so was a huge fuckup on his part. Regardless of what happens afterwards he absolutely needs to report the shooting himself.
If he had called it would have looked better than him fleeing the scene in terms of showing his innocence. However, I don't believe that there is a law that forces him to call police after either. Blind firing 8 to 9 rounds into a car is indicative of someone scared and shooting under fear/duress. Especially since only 2 rounds hit. Considering he was parked in the pump right next to the kids, that is close enough to make sure he would hit someone if he fired with the calm intention of hitting your target. In which case, he would not have needed to fire that many shots.
From the loose circumstantial evidence presented by the media thus far, I can see very easily how this could be a self defense case even if the guy was bit stupid in leaving the scene. He asks the kids to turn down their music, kids get hostile, a heated discussion occurs, the kids pretend to be packing heat and threaten him to make the guy run away. Instead their decision to scare him off back fires and instead of the guy running he pulls out his gun and shoots. In the moment of fight or flight instincts the guy decides to fight first then flight after. Perfectly reasonable psychological response. Or perhaps the kids were packing a gun and hid it afterwards. In which case, him fleeing the scene makes more sense as he might think those he missed after he unloaded his gun would try to shoot him.
However, it could be the kids just pissed the guy off enough with provocation and he went mental and shot the kids for their remarks. In which case he's guilty of manslaughter at a minimum and should rot in jail for his actions.