What takes a man to kill?

[Lady Macbeth]

Around August,1999 there was this news circulating every major channel in the UK about this farmer Tony Martin who was on trail for injuring two robbers who broke into his farmhouse with intent to rob him. He fired two shots at the robbers in the dark, hitting one burglar Fred Barras, 16, in the back and subsequently killing him and the other burglar Brendan Fearan in the leg and injuring him.

Apparently Toni Martin had taken his own 'stand' after he was burglarized quite a few times and the police failed to help him.
There was a lot of outcry from the UK public but the farmer was found guilty of murder and jailed for life, later, following an appeal his time was reduced to 8 years.

Its been some time since then and I believe the old man is out and about but I wonder was this killing unjustified?
After all in his own words he says....

I don't agree with shooting people. It's not something I take lightly. On the night of the burglary I was a terrified man alone in the house...
"I heard this murmuring and had this light shone in my eyes. All these things happened in a flash. I couldn't stand it any longer and then I just let the gun off.

"When you resort to using a gun you are desperate. I've never used that shotgun before. I'm not really interested in shooting rabbits round the house. I didn't even know if it worked. I discharged the gun and then ran upstairs

Now what must a person do to protect his home and family from invaders and crooks? He goes to the police and the police cant help him, he tries to put barbed wire around his house or buy a big dog to make his house secure and still they manage to get in.
In the end its all down to attack and scare them or be a victim yourself.