This appears to be the first self-defense shot by young green shirt boy. My understanding is green shirt boy is a runner for the group and may be carrying a medic supply bag. The person chasing him appears to throw something on fire at the boy before he is shot in the head and dies. Other people begin chasing the boy and knock him down he comes up shooting possibly killing skateboard attacker and blowing the bicep off another man who pulled a pistol on him.
In this video you can see green shirt shirt and the headshot victim.
Then green shirt is chased and shoots 2 more after they try to curb stomp him.