You'll be shocked when you find out that people had to pass through metal detectors and were not allowed to carry guns inside the event.
Nope. Open carry does NOT mean everywhere. It means you can be armed
as long as folks in charge of the location do not restrict it eg schools, sports events, rallies, airports, etc.
If anything, this showed how criminals won’t respect gun laws. The regular folks couldn’t carry, so they were left pointing at the criminal and shouting to the secret service, who failed to stop the shooter before his attempt. This won’t stop idiots from trying to use this as a gun control argument though.