Sounds like my old “mama cat”. She was the tamest cat you ever saw and very small, but release her outside and she was an avenging angel of death to any small critter she came across.
She even caught squirrrels big as she. And she often brought home live mice for my wife, who did NOT like it.
Years ago one of my kids brought home a cat (I love cats, hubby didn't like cats)and we were sitting in the living room with me reading a book and the cat on my lap...she suddenly sat up and looked toward toward the kitchen, jumped off my lap and about 5 minutes later came back into the living room with a live mouse in her mouth....She looked at me and actually growled like a wild cat. She then spent the next 45 minutes playing with the mouse. She'd put it down and the mouse would look dead and she wouldn't take her eyes off it. The mouse would suddenly come alive and run for its life and she would catch it again. It was a game for her and I didn't know what to do, called my sister as to how to kill the mouse, she said drop a heavy telephone book on it....Couldn't go along with that suggestion. Finally I got the broom and waited for the cat to drop it again and nailed it with the broom and using some wadded up plastic, picked it up and put it into a large medicine bottle, put the lid on and put it outside...Middle of winter in Michigan, it died. Must have made the cat happy that I got rid of the mouse. She came back and sat on my lap as I then continued to read my book......
She must have thought I was a poor hunter and was teaching me...in reality, I don't know if she really knew how to kill that thing,. I read an article later that said kittens have to be taught to kill by their mothers...