Part of the problem is our laws on murder. We have one degree of murder where in you set out to kill the individual. Anything else is manslaughter which is where you kill someone by accident. We need something in between where deliberate harmful actions lead to death even if death wasn't the intended result.
So manslaughter, aggravated manslaughter and murder. I am of course of the opinion that both the later should have the same sentence. I couldn't care less if you didn't think punching someone hard in the head would kill them, you still deserve to get banged up for a long time for it.
Actually, manslaughter and murder do both carry a maximum sentence of life imprisonment. The judges do have the power in law to sentence someone to life. They of course choose the actual sentence based on what they've heard in court.
I can't think of anything they might have heard in court, however, that would justify such a lenient punishment here. I know there are philosophical and sociological arguments about sentencing, prisons etc, but when you come to an individual case like this, they've sentenced someone to two years (basically) for taking away someone's life. It clearly wasn't an accident, and that is all that should be taken into consideration.