Since the deadly attacks on soldiers in Ottawa and Saint-Jean-sur-Richelieu, Que., there has been much discussion about the mental health of the attackers and the broader societal challenge posed by disenfranchised young men.
What we know is that Martin Couture-Rouleau ran down and killed Warrant Officer Patrice Vincent and injured another military man with his car before being shot dead by police. Michael Zehaf-Bibeau killed Corporal Nathan Cirillo at the National War Memorial before storming Parliament; he too was shot dead by authorities.
What we don't know is whether either man was mentally ill. Despite the speculation of family and friends and countless commentators, we will never know; you can't diagnose mental illness postmortem.
Besides, does it really matter?
Much of the speculation about the mental state of these two men implies that mental illness would somehow explain their bizarre behaviour and violent actions. We need to make the distinction between correlation and causation.
People who suffer from mental illness can be violent, just like those who are perfectly healthy can. But the underlying illness is rarely the cause of their actions.
There is no evidence that Mr. Couture-Rouleau or Mr. Zehaf-Bibeau suffered from a severe, untreated mental illness like schizophrenia, nor that either was psychotic or delusional. Even if they were mentally ill, there is no indication that they killed because of illness. In other words, they were criminally responsible for their acts.
This is a very different from a case like that of Vincent Li, the man who decapitated and cannibalized a passenger on a Greyhound bus. Mr. Li was actively psychotic and not aware his actions were wrong, so he was deemed not criminally responsible and hospitalized for treatment.
We know too that Mr. Couture-Rouleau and Mr. Zehaf-Bibeau were both attracted to radical elements in Islam, although the debate about whether they were terrorists or Islamic State-inspired jihadis can be left to others.
People with severe, untreated mental illness often hold extreme religious and/or political views. But, again, there is a distinction to be made: Not everyone who is extremely devout, or even fanatical, is mentally ill. You can't draw a straight line from mental illness to terrorism.
This is not to say there are no larger lessons to be drawn from these tragedies.
Much of the public discourse has been about the need to tighten security, to crack down on radical elements in society. But violence is not strictly a public security issue. It's also a serious and largely neglected public health issue.
We're probably healthier and safer than we have been at any time in history, but the spectre of violence and fear hangs over us. More than 1.6 million people die each year around the world in violent circumstances – about 815,000 suicides, 520,000 homicides and 310,000 deaths in armed conflicts (including terrorist attacks), according to the World Health Organization. (In Canada, there were 3,728 suicides and 543 homicides in 2012, the most recent year for which detailed data are available.)
A disproportionate number of these deaths involve young men. That is where some light needs shining.
Some of the information that's emerged about Mr. Zehaf-Bibeau's interactions with "the system" should give us particular pause. At best, he was a lost soul. At one point, he robbed a McDonald's using a pointy stick with the aim of being arrested, hoping it would help him kick a drug habit.
There are many other troubled, disenfranchised young men like him. They populate our prisons, our schools and our urban streets, not to mention the basements of many suburban homes, festering away playing Mortal Kombat. Almost none of them will end up being murderers or terrorists, regardless of their mental health status. But it's still a terrible waste. Our health, education, social welfare and economic systems are failing them.
In disturbing cases like last week, we want easily digestible explanations and quick, effective solutions. Sometimes, though, these don't exist.
The malaise and desperation that results in young men killing themselves and others is not going to be legislated or policed away. We are going to need at least as much compassion as crackdown.