The good news is that, in the last century, "only" 13 people have been known to be killed during the Pamplona run (although in just one year there were 113 injuries, including 16 serious hospitalizations).
Which seems about right for what is basically fleeing massive, irate, goring machines for fun.
Oh, and Pamplona is just the most famous of many Spanish bull runs. 2015 saw 10 deaths across the country, which matched a record set in 2009, because it turns out that antagonizing large animals made of muscle and rage can be dangerous (at least violent American sports have the courtesy to kill people slowly). Veteran bull runners attribute the problem to the same thing that can ruin any niche hobby -- reckless newcomers. New people show up, don't take the risk seriously, and get hurt, as Alex learned first-hand.
"When the race started, I made an executive decision to stop and wait until I could see some bulls. People were running past me and I kept screaming 'Come and get me motherfuckers!' I saw the front three charging at me through crowds of people and realized just how large they were. I (figuratively) s**t my pants and started smashing my way through people. And then I got hit. I felt like I got hit by a six-hundred-pound linebacker right in the small of my back. I guess one of their shoulders hit me hard enough to knock me down and I skidded on my knees for about fifteen feet. On cobblestones. That hurt like a b***h, and my knees were sliced to hell."