Given that location on the outskirts of town, near what look like natural or cultivated fields, I highly suspect Buddy and the rabbit were attacked by coyotes.
I live on the outside edge of a metropolitan area, with some similar area nearby and occasionally see individual coyotes in some of the natural walking trail parks here (especially at dusk). And when I take my own dogs out into my own yard at night, I can sometimes hear packs of coyotes whooping and yelping as they hunt at night down below the plateau I live on. The sounds send my two 60-lb dogs running for the door and I’m right there with them!
Around here, they typically kill small dogs, cats, and rabbits. But, when in packs, they will go after larger animals that are alone.