Like everyone else, De Swaan repeats, perpetrators of mass murder "have emotions, they construct meanings and justifications, no matter how hard they may deny it".
Thus Nazis regarded Jews and Gypsies as disease vectors, viruses contaminating Aryan society, which needed to be cleansed from such contamination - a metaphor that is repeated by perpetrators of genocide as widely apart as Cambodia and Rwanda.
Each time officers respond, they cross the threshold into the private lives of men and women, some of whom they have never met before, others who are repeat victims and perpetrators.
The majority of these perpetrators are repeat offenders, putting even more students at risk.
Research released last year that examined male college students who carry out these attacks suggests that about 1 in 5 perpetrators are repeat offenders.
Unfortunately, not reporting what happened increases the odds the perpetrator will repeat and perhaps even escalate his/her actions with others.
I am very passionate in expressing the need to stiffen laws and implement penalties that deter perpetrators from repeated violent conduct, and also serve as a warning to all abusers.
The crime has high rates of repeat victimisation and involves serial perpetrators; most women experience more than 30 instances of physical violence before they will report to the police any of what is being done to them, and evidence shows that if domestic violence is not taken seriously when it is brought to the attention of the authorities, this results in further and even lethal violence.
Their investigation also found that in most cases the victim and perpetrator were at least acquaintances rather than strangers, and that the perpetrators were often repeat offenders.
More than 150 writers from around the world, including Margaret Atwood, Salman Rushdie, Yann Martel and Colm Tóibín, have added their name to a letter condemning the deaths of three bloggers in Bangladesh this year, calling on the country's government "to ensure that the tragic events of the last three months are not repeated, and to bring the perpetrators to justice".
