Almost every year since 2004 in the US, a dog has shot a human. The Washington Post looked into such incidents after a dog named Trigger shot his owner over the weekend, and found 10 examples—and there could be more if the humans involved didn't report the shooting or seek medical care. The Post offers up a convenient chart showing, among other things, the dates of each incident and whether it was a hunting accident (yes, 50% of the time) or occurred in Florida (yes, 40% of the time). Many of the incidents involve things like dogs jumping into boats, a truck bed, or a regular bed and setting off guns laying there.
In one awful case, a man who was trying to shoot a litter of puppies because he couldn't find homes for them ended up getting shot himself when one of the puppies put its paw on the revolver's trigger; NBC News reported at the time that three of the puppies ended up dead but four survived and were to be adopted. Only one of the cases ended with a human death, in 2008 when a dog jumped onto a gun in the bed of a Texas hunter's truck, shot his owner in the thigh, and the man died of blood loss. During the same period of time, the Post notes, one cat shot its owner as well; that happened in 2005 when a cat knocked its owner's handgun onto the floor and it went off, Fox News reported at the time.