I have a video on my personal channel recommending to always charge an adoption fee for kittens if you are giving them to someone you don't know, not to give them "free to good home" because often, they don't get good homes that way. That goes for puppies too. A lot of times what will happen is some callous jerk will either feed the puppies or kittens to a snake (there are professional companies that sell humanely killed mice, rats, and rabbits for the purpose of reptile feeding, there's usually not a reason to feed live prey, especially not cats or dogs), or somebody will sell them to a laboratory (for a very small amount each, but an animal's pain means nothing to these people).
One reason I take animal cruelty so seriously, in addition to caring for the animals themselves, is that it often does lead, as in this case, to humans being hurt too (and a lot of times as in this case, people who murder start out by hurting animals).
I hope they catch this man soon before he murders anybody else.