Both the homeowner and shooter are responsible for this.  The shooter, however, put everyone within a mile radius in FAR MORE DANGER than he was exposed to in terms of any risk of a dog bite.  A terrible decision to shoot.  

I get the feeling of needing to protect, have two little munchkins myself.  

A similar event happened to me, except the 105lb. mastiff actually attacked, and it was not on its property.  Pinned him to the ground with my hands.  I got a nip and a few stitches, my dog had to have reconstructive surgery.  

Mentally mature gun toter's know what a credible threat is, and just as importantly where and where not to shoot.  Unfortunately, immaturity is not a constraint within the 2nd amendment.