Being new here we don't know each other but I can tell you are a loving, caring Mommy and would not ever do anything that you knew would cause harm to your furkid. Don't be so hard on yourself. We have all had something happen at one time or another and it's just one of those things.....an accident.
The same thing had happened to my Nikita. She was out on her rope and saw a squirrel and off she went and ....well you know what happened. I was outside with her but couldn't do anything to stop it. Cheer up and forgive yourself for something that wasn't your fault.

Lots of Hugs
Monty, Kiki and Deb