This guy is going to face serious problems because of few seconds of rage. What he did is wrong but he was very unlucky too. From the reports, looks like he hit the victim only once: out of frustration or anger. I'm sure he didn't want to hurt him seriously, let alone killing him. Is a sad and unlucky story for all those that are involved.
Utah teen charged with homicide by assault in soccer referee death, avoids manslaughter count. Ref. USAToday
Well, if you are right about the two years detention, that's enough in my opinion. This is a tragic accident, not a murder. The guy will pay but still being able to live his life when outside and restart from zero. He made a big mistake but he is not a criminal or a danger for the community: just a young lad that got carried away and that has been terribly unlucky.