http://www.airgundepot.com/popular-pellet-rifles.html
I have not shot a pellet gun since I was around 13 years old, but looking at some of the products on the above linked site; it seems that a pellet fired from some of these guns would travel quite far and would probably kill a pet outright if hit from 10 yards or less.
This could have been an accident depending on KathieI's home layout.
I still have a scar on my pinky finger from where a fellow 13 year old shot me with his BB gun. That was from about three feet and the gun had not been pumped up that much. That was not an accident though just a punk with a gun.