What exactly is a humane death?

So the topic comes up from time to time on a death being inhumane. One notable charge came about after public outcry after some crazy asshole blew up his dog. Now one could make the argument that this is a horrible needless death that deserves to be punished but I will ask the question what exactly are we punishing? What should this punishment look like in a just society?

Without a doubt this lab died nearly instantly. That is without dispute. This dog died in a shorter span than the average dog being blue juiced at the vet or gassed at a crappy southern shelter. Which begs the question of what is a humane death and what is cruelty?

My state is pretty clear that first degree animal cruelty is causing the death of an animal with undue suffering or screwing one or being a party to either of those actions.

The humane slaughter act requires either an instantaneous death or some kind of stunning before being killed except as religious exemptions are applied.This dog was not being slaughtered but again, instant death.

I'm not saying that this was a good thing  but our laws are pretty clear on what is legal and what is illegal. You do have the right to kill your own dog except as exempted by law as long as you use a method that doesn't cause undue suffering.  For the better part of the history of mankind this was done with a axehandle or a bullet. Hard pill to swallow for many but let's examine this pill.

Death makes people uncomfortable. A not pretty death or sterile death makes people very uncomfortable. This is the aesthetics of being in the first world where the best way to die seems to be in an opium induced coma in a clean music filled room. If death could be nearly instant and if you didn't understand it was coming is it really cruel?

I think the true objection is twofold - people abhor a waste of life. We can easily accept the mass slaughter of chickens, pigs, and cows because it serves a purpose. We go out of our way now to make the slaughter process neat and tidy and most importantly out of sight. Second is the idea of a messy death - even if instant is somehow more wrong than a sterile one even if it is out of the sight of someone else. Even if in a bed - the end is almost never as nice and neat as one would hope for someone they care about.

I am glad to say the loon in the story above plead out. I assume because he had either a lawyer who was either incompetent or thought the greater social good would be served if this guy never had a pet again. I don't say this because I think he did the right thing or did nothing wrong.  There is a ton wrong with this story from explosives to the end of what was described as a very sweet dog but the justice system is not a popularity contest.