You know this HOW ?
Good reason to stab and kill owner too ?
No, the guy is a wacko wanting to kill someone. He goes after an older lady and kills her, but her dog is yapping and nipping at him for the attack, so he stabs the dog.
It’s not rocket science. I don’t think it’s plausible he was only trying to kill the dog and wound up killing the lady, because the story says he first tried to stab a guy.
Do you have a different insight?