One of the strays I took in about 2 years ago started being agressive towards my other kitties. He was vet checked when I took him in, neutered, up to date on shots and tested for all of the feline diseases. Now he is showing this agressive behavior and seems to want to be outside so I have let him back out the past 3 nights and each morning he has left me a present right outside the front door, a dead mouse! 3 days, 3 mice! What is up with this? Does anyone have any idea?