Sounds like a nightmare of an investigation. There's a lot more story there than can be researched and put into a news column. It sounds like he was pushed to his breaking point and wasn't in his right frame of mind. Killing seemed like a reasonable answer and once someone is there, it's safe to say reality is going to skew quite a bit.
As far as a life for a life that's a touchy subject. To me, the person hasn't paid for their crime if you kill them. Not really. A punishment should be something you have to live with afterwards. To be killed in the process defeats the whole idea. It certainly doesn't act as a deterrent. Once you've skewed reality so far as life has no value and killing a person is no more serious than swatting a mosquito, you aren't in a place where you'll consider the local laws for murder. Because it's not murder to you anymore. It's solving a problem and problem solving isn't a crime. It doesn't become murder to you until after it's done. Then reality straightens out and you can identify what you have done and that it was wrong. The problem is you can't go back.
Now premeditated murder that was planned and carried out with intent to kill may be deterred by the threat of being executed if you get caught. But then no one ever plans on being caught. So if you're going to get away with it, how can you be punished? If people planned on being caught, there wouldn't be any crime at all.
"A woman is a woman, but a good cigar is a smoke"
- Rudyard Kipling