Mass murders are becoming a depressingly familiar routine in the United States — we can now expect to experience a media grabbing shooting about once a month. And the frequency can only increase as future cohorts of copycat killers are spawned by the seductive opportunity to temporarily gain the spotlight.

Amidst the anguish and heartbreak felt by the victims’ families, there are always two haunting questions. What motivates someone to kill strangers wholesale in a seemingly senseless way? And what, if anything, can we do to stop these tragedies from recurring?

The accumulating large sample of mass murderers and their eagerness to explain themselves in print and videos provides a rich data base. Dr. James Knoll, a leading forensic psychiatrist with special expertise in mass murderers will describe the pattern of their demographics and psychological profiles.

Dr. Knoll writes: “In 2013, the Congressional Research Service (CRS) issued a report on public mass shootings. The CRS used as its working definition incidents “occurring in relatively public places, involving four or more deaths.” The CRS identified 78 public mass shootings in the U.S. since 1983 that had resulted in 547 deaths and 1, 023 casualties.

Most perpetrators are young males who act alone after carefully planning of the event. They often have a longstanding fascination with weapons and have collected large stores of them. The shootings usually occur in a public place and during the daytime.

Individual case studies involving psychological autopsy and a careful analysis of the often copious communications left behind suggest common psychological themes. The mass murderer is an injustice collector who spends a great deal of time feeling resentful about real or imagined rejections and ruminating on past humiliations. He has a paranoid worldview with chronic feelings of social persecution, envy, and grudge holding. He is tormented by beliefs that privileged others are enjoying life’s all-you-can-eat buffet, while he must peer through the window, an outside loner always looking in.

Aggrieved and entitled, he longs for power and revenge to obliterate what he cannot have. Since satisfaction is unobtainable lawfully and realistically, the mass murderer is reduced to violent fantasy and pseudo-power. He creates and enacts an odious screenplay of grandiose and public retribution. Like the child who upends the checkerboard when he does not like the way the game is going, he seeks to destroy others for apparent failures to recognize and meet his needs. Fury, deep despair, and callous selfishness eventually crystallize into fantasies of violent revenge on a scale that will draw attention.The mass murderer typically expects to die and frequently does in what amounts to a mass homicide-personal suicide. He may kill himself or script matters so that he will be killed by the police.

The frequency of mental disorders in mass murderers is controversial because it is not clear where to draw the line between “bad”‘ and “mad.” The paranoia exists on a spectrum of severity. Some clearly do not meet criteria for any mental disorder and often may justify their acts on political or religious grounds. Others have the frank psychotic delusions of schizophrenia. Many perpetrators are in the middle, gray zone where psychiatrists will disagree about the relative contributions of moral failure versus mental affliction. Thanks so much Dr. Knoll for clarifying our first question on the demographic and psychological factors that help explain what motivates the mass murderer.

Which brings us to our second question. Now that we know what mass murderers look like, can we use this knowledge to prevent them from becoming mass murderers?

For the most part, the answer is a disappointing no because it is just not possible to find needles in haystacks.

Lots of people fit Dr. Knoll’s demographic and psychological profile, but never act out their fantasies. We can easily predict a high-risk group, but have no way to identify the one specific person who will go haywire, and when it will happen. To prevent the act of the killer who winds up pulling the trigger, we would have to seriously violate the civil rights of the hundreds of thousands of others who resemble him, but turn out to be harmless. Mass murders happen way too often for us to tolerate, but way too rarely to be easily preventable by identifying and isolating the mass murderers. We can’t possibly jail or hospitalize everyone who has violent fantasies.

The best we can hope for is to reduce access to weapons of mass destruction. It shouldn’t be easier for a potential killer to get a gun than get an outpatient appointment. We need to improve both sides of this equation. More treatment, fewer guns.

The only good outcome of the mass murder epidemic has been an increased awareness that mental health treatment is woefully underfunded and inaccessible to most people who desperately need it. It often takes months to get an outpatient appointment and beds are so few that getting into a psychiatric hospital is almost impossible. Improving accessibility to mental health services is a national necessity and may help prevent an occasional tragedy — but it is only a very partial and totally inadequate answer.

The much more effective step is a responsible gun control policy that balances the civil rights of individuals with the safety of the public. It is no surprise that a majority of the population (including a majority of gun owners) favors measures that would restrict high-risk individuals from having such easy access to guns. The only surprise is that the majority of reasonable people can be held hostage by the minority radical faction of the NRA, by the free spending arms makers who sponsor it, and by craven politicians.

For a balanced analysis of the civil rights issues that should be considered in framing a fair, safe, common sense gun control policy, see this article.

The way forward is clear — we need to reduce free access to guns for those individuals who are at high risk to use them irresponsibly. Undoubtedly, this will eventually happen as the mass murders continue to pile up. Sooner or later, public outrage will overcome the NRA radicals and push politicians to do their job. But how much more blood must be spilled before simple common sense prevails over extreme ideology.

Allen Frances is a psychiatrist and professor emeritus, Duke University.  He blogs at the Huffington Post.