Yeah, he's doing what he was created to do. If he/she kills, it's with no malice as would a human, they're either scared or hunting, that's their nature. It is too bad if someone gets mauled or killed....and the outcome can be even worse for the mountain lion when that happens.
When I think about all of the mountain lion attacks I've heard about, most often if the person had a gun they missed their target and the shot didn't deter the lion. It isn't easy to properly aim and fire a gun when a lion is charging you or is about to take a bite.
Which is precisely why I named an 870P as my choice for big QittyQat defense...
As a conservative rule of thumb, you can expect buckshot patterns to spread 1 inch per yard. In other words, a buckshot pattern at 15 yards should be about 15 inches.
This is as much the result of habitat encroachment as wildlife conservation law (as many might have you believe). Growing up here I NEVER saw deer, and we lived in the woods when I was a kid. Now the deer are everywhere, day and night. They've simply run out of woods and stuff to eat.
We have a very narrow sidewalk that runs in front of our house. This mountain lion was seen walking on our sidewalk last night just before midnight. It was last seen walking down the hillside to a much more populated area of houses.