Holmes was prepared for a gunfight; he was protected better than most SWAT teams. Not sure the typical consumer-grade ammo would have even slowed him down.
Even if he did have civilian ballistic armor, the backface trauma from a solid torso hit on it -- even from a 9mm -- is an extremely painful and bruising shock (and may include broken ribs)...
Even with armor, a few rounds into his torso and/or whacking on his helmet would have distracted, slowed, and disabled him enough for folks to tackle and disarm him.
But he lacked armor; those same torso hits would have dropped him.
Even if he did have civilian ballistic armor, the backface trauma from a solid torso hit on it -- even from a 9mm -- is an extremely painful and bruising shock (and may include broken ribs)...
Even with armor, a few rounds into his torso and/or whacking on his helmet would have distracted, slowed, and disabled him enough for folks to tackle and disarm him.
But he lacked armor; those same torso hits would have dropped him.
Am good friends with an avid shooter, ballistics expert who loads his own ammo and uses a chronographer (I think that's what it's called!) to measure load force, and has kept detailed logs of this stuff for years, and a retired LAPD watch commander. He's dismayed at the roll-over attititude of folks who think that body armor made the shooter unstoppable. This friend says that a .45 slug full load 230 grain bullet, at 950 feet per second, hitting that armor, would hit the body armor with about the equivalent force of a steep pipe whacking the wearer but good and hard. It would probably knock him down completely; it would assuredly make him stagger. If one, two, three CCers in there armed with .45s, locating the guy by his weapon's muzzle flashes, had hit the shooter, he'd have gone down. The .45s wouldn't have killed him or penetrated the armor, but they sure would have knocked him silly.
This guy, an experienced cop in a rough part of town, said this guy wasn't dressed that way in preparation for a gunfight -- he was dressed that way to keep himself from being killed by police when they finally showed up. In my friend's experience, which spanned a couple of decades, guys like Holmes never expect civilians to shoot back.
I've shot enough .45 rounds at 1/2 inch steel targets, in company with this guy, to believe him about what would have happened to Holmes ability to remain standing, armor "better than most SWAT teams" notwithstanding, if he'd been barraged by a half dozen rounds from a couple of .45s.
Concealed carriers, especially those armed with .45s, would very likely have saved many lives and injuries. Body protection or not.