How did the 'smoke in the face' incident lead to Danny getting shot? Is this really grounds to kill someone?
Blowing smoke into someone's face is an insult. It means you do not respect them, nor their space (which can mean territory). Consider the deaths of people who inadvertently wore the wrong color(s) in a gang territory.
In some gang-member's minds, it does not take much to warrant injuring or even killing someone. Protecting your integrity and the integrity of any others you represent is the definition of being a member.