Either he is lying about why he shot her or he is a criminally negligent dumbass that violated the most basic rules of hunting. Either way he should be prosecuted.
Of course someone in the left wing media is going to blame the NRA, but that is like blaming defensive driving instructors for drunk drivers.
The local Buffalo News gives some specifics, including a Google Maps image identifying the site. The shooter resides in the town of Sherman, and was about 2.5 miles from home. The site is along Armenian Road, just out of town, and one can surmise a likely location of the Billquist residence. It seems likely she was walking the dogs along the perimeter of a plowed field behind this residence, and the shooter was across the field, perhaps on the perpendicular edge, but at any rate sighting against the wooded perimeter. I would have to suppose that this was his habit of hunting.