Luck of the draw, I guess.
Pistols sometimes hardly work, at other times they outperform our expectations. Sometimes even a .45 hardly deos anythng to someone, then there are other times it goes clear through your targets chest and kills an innocent bystander way down the street.
Bullets do weird things and are hardly predictable no matter what the jello says. A while ago a police officer was trying to shoot a birdfeeder, he missed, bullet sailed through a wooded area, and nailed a kid in the head a good distance away. What are the odds of that?