A couple thoughts
There are a few things that most, if not all, of these shooters have in common.
1) access to guns (not always legally)
2) on some sort of Psychotropic drug/serotonin reuptake inhibitors (SSRIs)
3) are suicidal
4) somewhat of a loner, and seek recognition.
1) guns have been around for ever and even assualt weapons have been accesible since the 50s, for US civilians. As I understand the previous "assualt weapons ban", the number of mass shootings did not decrease when it was implemented, and did not decrease when lifted.
2) Psychotropic drugs are being used more readily, for kids to adults. One of the side effects of these drugs can be depression, suicide and hallucinations. All 3 "side effects" can also be observed if the "patient" stops the usage etc.
3) suicidal before, or after the drugs?
4) being a "loner" might lead to the depression, but IMO, being a loner, might not be their choice, but an external factor, caused by someone else, which may, or may not affect the person emotionally/mentally.
Seeking "recognition/notiriety, is why I think they seek out those that can not defend themselves, like those in "gun free zones". When confronted, most attempt to committ suicide, because they want to maintain control and not have someone else decide what happens to them.
The "Batman killer", had 7 theatres within 20 minutes of him, that were playing Batman that night. He chose the only one that did not allow permit holders to carry.
In the last 50 years, "mass shooters", have not killed more than 3 people, in locations that permit holders were allowed to carry, except in Arizona, in the Giffords shooting.
So, what DON'T they have in common, with the people that do not kill, when they have the same access to guns?
And what has changed in the last few decades, to increase the number of these mass shootings?
2012:
Suicide now the leading cause of injury-related death in the United States
The conventional treatment for suicidal tendencies is almost exclusively prescription antidepressants. Antidepressants are the second most prescribed drug class in the U.S. (second only to cholesterol-lowering drugs). More than 253 million prescriptions for antidepressants are filled nationwide every year.
Studies have repeatedly demonstrated, however, that antidepressants are no more effective and in some cases less effective than a placebo. A study in the January 2010 issue of JAMA concluded that there is little evidence that SSRIs (the widely-prescribed group of antidepressants that includes Prozac, Paxil, and Zoloft) benefit people with mild to moderate depression. The researchers stated, "The magnitude of benefit of antidepressant medication compared with placebo... may be minimal or nonexistent, on average, in patients with mild or moderate symptoms." SSRIs were found to be only 33 percent effective, the same as a sugar pill – but with significantly more adverse side-effects, including violence or suicidal thoughts and actions.
And what else has happened since the 50s/60s?
Deinstitutionalisation, of these "patients". Drugs have become the perferred method of treatment, which may or may not always work with every individual.
If a drunk driver kills someone, or many, while drunk and behind the wheel, does it make sense to restrict, the "weapon" he/she used to kill, for everyone with access?
Or if a person has a health problem, that would not allow them to operate a motor vehicle safely, should he/she, be prohibited from driving?
IMO, access to the "weapon", is only one piece of the puzzle. And any "ban" can be perceived as a "punishment" on all, for the sins, or sickness, of a few.
And then we can go back to Soap's post and discuss whether secural or sacred authority is the answer, but IMO, that is a non starter with the "left". They are only interested in expanding secular control, through government.