I was not going to comment in a political context on this tragedy until I saw the following:

New York Mayor Michael Bloomberg, a long-time advocate ofgun control, called on both candidates to address what they would do to help prevent such tragedies.

“No matter where you stand on the Second Amendment, no matter where you stand on guns, we have a right to hear from both of them concretely, not just in generalities --specifically what are they going to do about guns?” Bloomberg said today on WOR Radio. The mayor is founder and majority owner of Bloomberg News parent Bloomberg LP.

Gun control is why this murderous assailant managed to kill 20 people and nobody had a crack at shooting him, as they were unarmed.

Let's look at the facts of this event.  Metal detectors and searches would have done nothing to prevent this, but would have treated every patron as a felon.  The assailant came in through a back door, which means he tampered with a crash-bar equipped exit at some previous time or had "help."  Those exits are necessary for fire safety purposes.

Reports are that the assailant was wearing body armor.  This would have made him much more difficult to shoot and stop for an armed citizen, but body armor is not "bullet proof"; it is bullet resistent, and if you take a round in the chest while wearing it the energy is still dissipated on your chest -- it just doesn't make a hole.  Continuing to shoot people while being punched in the chest (pretty much what the shooter would be experiencing) would be difficult -- but not impossible.

The presence of a bunch of openly-carried or concealed weapons might have done nothing.  A pistol against a guy toting a rifle or shotgun is not a "fair fight" but it beats nothing, which is what the victims had.  The option to fight back is better than no option at all, whether you can or do choose to use it or not.  Oh, and let's not forget that it appears that Cinemark, the company that owns the theater, appears to prohibit by policy law-abiding citizens carrying concealed weapons.  If the assailant knew this (and it is, apparently, posted on signs at the ticket counter of at least some of their theaters) then he knew that every patron in the place was literally a walking target unable to defend him or herself as law-abiding citizens are disarmed by signs -- but criminals are not.

We do not know what the shooter's beef was with the theater or the people in it.  We will likely learn at least some of that in coming days and weeks.  The alleged shooter is in custody and reportedly has no prior criminal record, so clues are not to be found there. 

The simple fact of the matter is that there is a tiny percentage of people who are cracked in the head.  Walking into a theater armed to the teeth and carrying incendiary devices to intentionally drive people to where you can more-easily shoot them is the act of a depraved mind and evidences obvious premeditation and intent.  The criminal justice system will mete out the punishment it is able for this circumstance, which will be wholly inadequate as you can only take a murderous thug's life once with capital punishment.

The Second Amendment and fully-recognized Constitutional Carry is the only means available to mitigate these sorts of events.  Firearms and smoke bombs are neither difficult to acquire nor can they be made difficult to acquire or even construct for someone with murderous intent, and as such the idea that "gun control" will ever do anything other than disarm law-abiding citizens is the worst sort of crap argument from ethically and morally-bankrupt fascists who themselves employ armed security around them at all times.

Mayor Bloomberg can pontificate on whether Constitutional Carry should be prohibited and the Second Amendment amended, which is the only lawful means to alter it, if and when, and only if and when, he dismisses all of his own armed security and turns over his own firearms -- all of them.

Until then, Mayor, you're a jackbooted ******* politician trying to exploit the death of people at the hand of an obviously-deranged individual and need to shut the **** up.