The barbarians have gathered, it would seem. Let's just mutilate people for stealing some sweets from a shop. Maybe bring back public hangings. Oohh, I know, random executions!
Good lord.
He took things into his own hand, used excessive force and violence to bring revenge on a fleeing criminal. He deserves his sentence.
That said, justice and revenge do not mix. People who think revenge = justice are deluded.
Edit: I see a lot of people are basing their reactions by placing themselves in the position of the sentenced, that is flawed.
That's not to say I wouldn't react the same way, but I would still be deserving of a 30 month jail sentence.