We're still getting information and surely will not know everything for days yet, but the initial report is that there was an armed officer on duty, and he fired at the attacker.

[url]http://www.nbcnews.com/storyline/orlando-nightclub-massacre/orlando-nightclub-shooting-emergency-services-respond-reports-gunman-n590446[/url]

[Orlando Police Chief John] Mina said a uniformed officer working extra duty exchanged gunfire with the shooter, who officials say was armed with at least two firearms.

"The officer engaged in a gun battle with that suspect. The suspect at some point went back inside the club and more shots were fired. This did turn into a hostage situation," Mina said.

So reports say that someone else was carrying a firearm, legally, and he fought back.

Yet we are still looking at what is the worst mass shooting on American soil.