Putting things out of their Misery

A few minutes ago, there was a mouse outside my
house. It obviously had taken poison as it was slowly
shuffling around and kept falling over itself. It looked
like a young mouse as it was quite small.

I decided that it had to be put out of its misery as it
was clearly in a lot of pain due to the poison drying
out its insides.

Yet what is an acceptable method of killing a rodent as
quickly as possible? Could I bash it with a stick? Squash
it with a rock? Or throw it into a fire?

I decided that none of these methods were fast enough so
I resorted to my trusty firework collection. I used a Black
Cat and placed it beside the dying mouse and lit the fuse.
It was all over in a matter of seconds and I wont go into
the details but what I can say, is that the mouse definitely
died instantly.

A while after the incident, I kinda felt guilty. But didn't I do
the animal a favor? Sould I have left the animal to die in pain?

I don't think so.