The chance of getting caught is so low, and the consequences of being caught are so unreliable that I'm sure these two did not even calculate being caught. Didn't even consider it could be the wrong target.

How do you convince two kids, who don't think they will live past 25, care about nothing but their friends and their image to weigh the consequences when they don't believe there is really any chance the consequences will happen?

6 angle of HD footage on every inch of public property?
Audio recordings of all public areas?
Directional Bullet sensors?
Violate constitutional law and also punish their families?
Violate constitutional law and allow onsite summary judgement to avoid lawyers?
Declare all gang members terrorists and not worry about their rights?
Put a Cop on every block to sit and wait for bad things to happen?
Give everyone a concealed weapons permit?
Reduce student/teacher ratios to 1:8 and give them tools to enforce home enforcement
Make teachers liable for ethics and moral?
Serial numbers on every bullet with liability to original purchaser?
Possession of Gun results in onsite and immediate capital punishment?
Raise property prices so much that all the "undesirables" move and become someone else's problem?
Make Parents personally & criminally liable for actions of children?
Sterilize violent people?
Capital Punishment for ALL drug offenses?
Legalize all drugs so there is no money in trafficking it?
Provide all low income parents with government jobs with better pay and benefits?
Put trackers on all first time offenders until 20yrs past last crime?

As you can see, really none of these options are good, none will get the support of a majority. At the same time, crimes like this cannot be seen as "one time events we deal with after the fact" Proactive approaches must be taken.

Sad on all accounts for all parties :-(