Waiting for the justice system seems to be the right thing to do but a lot of will not blame him for getting a revenge in such a situation.
In the real world, he still has to have a trial by his peers for the final judgment to be sentenced for a crime. Both the prosecution and defense can excuse a juror until all slots are filled.
So, it's very unlikely that all jurors would find him not guilty, at least on the major time-serving and highest crime prosecuted. That's why in most cases there are secondary charges that aren't as bad and don't add as much time.
For example, there could be the "lifetime" crime of Aggravated murder 1, but also Murder 1, and for one of them to stick for the most time added to sentencing, another felony such as Fleeing the scene, Knowingly concealing or disposing of a corpse, etc. which could by themselves be 2-5 years, but added with a/n Aggravated murder/1, make that a life to 20+ to life sentence.
That said, there are trials by insanity, which could come into play and would institutionalize them until they are rehabilitated if found guilty by insanity.
Another thing that isn't discussed far enough in the criminal justice system is something called jury nullification wherein a jury can find a defendant not guilty of the crime(s), even though they believe that they are guilty.
Reasons for jury nullification could be:
- The jury believes the law is unjust
- The jury believes the prosecutor misapplied the law
- The jury believes the punishment is too harsh
- The jury is frustrated with the criminal justice system
- The jury has prejudices in favor of the defendant
- The jury wants to send a message about a social issue
So, even though the jury knows someone guilty of Murder 1, they are completely let off in the event of jury nullification. And, because we have the 5th Amendment in the United States, there's protection of double-jeopardy, where they can't be recharged for the same crimes. So, they're essentially free to go.