What is a good prayer for after killing an inocent animal?

a snapping turtle bit my curious puppy on the lip. She started bleeding like crazy and i did not know where she had been bit or how severe. While my brother tended to her i smashed the turtles shell in with a big rock. I have never seen anything suffer more in my life. It is now the next day and i still feel like shit. Could someone either give me a prayer or something that will make me feel better or at least take my mind off of it.

Rub a dub, dub…….. thanks God for the grub