Recently, the parents of Cheng Chieh, the 21-year-old Taiwanese undergraduate who stabbed four people to death and wounded 24 others, made a very public apology on their knees. There was a wave of anger towards the parents.
The general sentiment in Taiwan over last month's incident was that Cheng Chieh's parents were responsible in some way, and should be held culpable. In the words of the mother of one of the victims, they "did not teach him well".
Holding parents accountable does not appear to be merely a Chinese predilection.
Take the Columbine High School shooting in the United States in 1999, in which a pair of young gunmen killed 25 people and injured 24 others, before turning their guns on themselves. A subsequent poll found that 83 per cent of Americans believed the parents of the two shooters were partially responsible because they failed to teach them "proper values".
It is perhaps understandable that in such nightmarish situations, we need to explicate the incomprehensible so that the world would at least seem less arbitrary, frightening and senseless. At the same time, there is also a need to have an identified source at which that collective sense of outrage can be directed. But the inconvenient truth is that such things are never that simple.
Coming on the heels of that murderous spree in Taiwan was the similarly murderous rampage by 22-year-old Elliot Rodgers, who last month killed six people in California.
Then there was Adam Lanza, who one day in December 2012 shot dead his own mother, 20 schoolchildren and six adults in an elementary school in Connecticut before shooting himself in the head, as did Rodgers.
From the accounts that emerged subsequently, it was apparent that both Rodgers and Lanza had been mentally unwell since they were very young.
Lanza was diagnosed with Asperger's syndrome - a disorder that the American Psychiatric Association has recently subsumed into the wider category of autism spectrum disorder. The same diagnosis was suggested for Rodgers.
The parents of both these young killers, though divorced, were certainly very much involved in their upbringing - the mothers, in particular, went to great lengths to do what they could to help their sons.
Cheng Chieh, by his own admission, found life "empty and not worth living" but was too fearful to kill himself. With that warped and perverted logic, he proceeded to kill enough people so that he would receive the death sentence.
Professor Paul Appelbaum, a forensic psychiatrist at Columbia University, sees such cases as "suicides with murder as an epiphenomenon, rather than murders that happen to end in suicide".
Mass killings are relatively rare. As the number of mass murderers is small, and most either kill themselves or are killed by the police, it is difficult to make any proper study of them. In grappling for an understanding, one usual and almost reflexive postulation is that the perpetuator is mentally ill.
Mental illness and violence
THE connection between mental illness and violence is almost inevitably invoked in the aftermath of such tragedies. For those of us who are mental health professionals, this is never an easy thing to talk about.
The discussion can be fraught with difficulties, and conflating violence and mental illness in the same sentence can increase the risk of further stigmatising people with mental illness who are already much discriminated against and marginalised.
We would emphasise that most violence has no relationship to mental illness, and that is a statistical fact. We also like to point out that most mentally ill people are not violent; most violent acts are not committed by people with mental illness; and people with serious mental illness are more likely to be victims of violence than perpetrators.
And that the most common form of violence associated with mental illness is not against others, but rather, against oneself.
But this is contrary to what the public usually believes. A study published in 2007 showed that 38 per cent of the public in Singapore believed that mentally ill people are dangerous.
A more recent surveyfound that almost half of the respondents believed that people with serious mental illness are more dangerous than the general population.
That said, we also cannot deny that there is a small proportion of people with serious mental illness who can be violent; denial of this does not do those with mental illness nor our larger society any good. Violence is indeed more likely during an episode of untreated psychosis, especially if it is associated with paranoia and so-called "command hallucinations", which are voices commanding a person to do certain things.
The potential for violence rises sharply if there is concurrent use of street drugs. Another risk factor is a history of victimisation. As the poet W.H. Auden so succinctly put it in his poem September 1, 1939: "Those to whom evil is done, do evil in return."
JUST as everyone would want some sort of satisfactory answer in the wake of a mass shooting, there is no doubt that the parents of these killers would also want to know why.
It is difficult to imagine what sort of hell the parents of the killers have to live in, in the aftermath of these heinous crimes.
There are two particularly affecting and detailed essays on this subject. One was written in 2009 by the mother of one of the Columbine shooters, Susan Klebod. It was published in O, The Oprah Magazine. The other is an article this year in The New Yorker, which was based on a series of interviews given by the father of Lanza.
Both accounts are riven with grief, parental guilt, bewilderment and the almost unbearable agony arising from the suffering of the bereaved families. Both described the somewhat similar trajectory taken by their sons - the inability to fit in at school, the social ineptness, and the progressive alienation and isolation.
In a Congressional Neuroscience Caucus in the US House of Representatives convened last year to discuss the link between serious mental illness and violence, one of the experts called was Dr Elizabeth Childs, a child psychiatrist. She described two children with the same illness whom she had treated. One later killed his parents before killing himself, and another recovered and went to college.
Reflecting on the very different outcomes, she said that "persistent isolation" often leads one down the path to tragedy.
While engagement with mental health services presents the best opportunity to help these alienated individuals, it is also the singularly most difficult task, particularly when the patient, family and community are in denial.
There are many young men who are socially isolated, angry and unhappy, and who may or may not be mentally ill.
Predicting who among them would eventually kill is next to impossible. The title of Susan Klebold's essay is I Will Never Know Why.
In the concluding paragraph, she writes: "I think I believed that if I loved someone as deeply as I loved (my son), I would know if he were in trouble. My maternal instincts would keep him safe. But I didn't know. And my instincts weren't enough. And the fact that I never saw tragedy coming is still almost inconceivable to me."
It was reported that Lanza's DNA is being sequenced to see if there might be some aberrant genes or neurological abnormalities.
While science might in the future help us to better predict violence, I doubt if it could ever be able to provide a complete understanding of such monstrous acts of abnegation of self and others.
Our search for the true and complete meaning, I think, is like the journey made by Marlow, the protagonist in Joseph Conrad's novella Heart Of Darkness, to look for the sinister Mr Kurtz.
What he found at the end of a gruelling journey was a dying man who had become murderously corrupt. In Marlow's words: "His was an impenetrable darkness. I look at him as you peer down at a man who is lying at the bottom of a precipice where the sun never shines."
Of what had happened to him, Mr Kurtz could only whisper at the moment of his death: "The horror! The horror!"
The writer is the vice-chairman, medical board (research), at the Institute of Mental Health.