A 50-year-old German man, Andreas N., deliberately drove his car into groups of foreign-looking people on New Year's Eve — first in Bottrop and then in Essen — before police could apprehend him. He injured eight people during the rampage. Currently, he is in police custody. Authorities assume his actions were racially motivated. Moreover, the welfare recipient and Essen resident is said to be mentally ill.

Deutsche Welle: Seemingly racially motivated car attacks recently carried out by a 50-year-old German man in Bottrop and Essen have captured the attention of authorities and citizens alike. What might have driven the perpetrator to carry out his New Year's Eve attacks?

Britta Bannenberg: We will have to wait before we can say with certainty. But initial indications point to a typical behavioral pattern. Young perpetrators are different from older ones, for instance. And there are a number of distinctive features among older perpetrators.

Such as?

Most perpetrators are not well psychologically. They commit similar serious crimes, such as grievous homicide, but their psychological problems are quite varied.

Nevertheless, we have discovered that more than one-third of grown perpetrators between the ages of 24 and 70 showed serious signs of severe psychological illness, such as paranoid schizophrenia. As a rule, the targets of their attacks — which often claim the lives of several individuals — are foreigners. The people who carry out such attacks are often filled with resentment, hatred and hostility toward society.

They tend to project their hate onto specific groups of people, whether foreigners, women, colleagues or society in general. Psychological disorders like schizophrenia are madness-inducing diseases that bind elements of psychological illness with that renunciatory hatred.

That is what makes such people so dangerous when they decide to take revenge on society by injuring or killing other human beings.

Are there ways to recognize such dangers early on, perhaps even preventing such attacks before they can be carried out?

Yes, of course. Empirical research has shown that quite clearly. Although it isn't possible in every case, it is in most. It is also important to add: One-third of adult perpetrators, as I said before, suffer from psychological illnesses such as schizophrenia — a serious psychological disease very different from other personality disorders.

Still, people with personality disorders are dangerous in other ways. They are likely more cognizant of what they are doing, they may even be able to control their actions. Nevertheless, they often become just as obsessed with the idea of carrying out a spectacular murderous attack, hoping to kill as many people as possible. Those are the two variations that we have found among lone perpetrators and those who run amok.

It is certainly possible that people with direct contact, such as neighbors or work colleagues, might notice such disorders and notify police early on. It increases the chances that these people can be found before they can commit a crime. Schizophrenia, for instance, can be treated medicinally. Left untreated, the threat of violent behavior is seven to eight times higher than normal, and when alcohol or drugs are added to the mix the risk jumps some 14 times. But if those with such illnesses receive medical treatment the risk is once again reduced to normal levels.

Are there clear conclusions that German officials should draw from attacks in which perpetrators suffer from schizophrenia or other personality disorders?

Societal awareness, not only for people who may be ill or psychologically conspicuous but also for those who utter threats or voice violent intentions, must be cultivated. Those who show great interest in carrying out violent attacks or are overly interested in violent crimes or acts of terror usually display their hate months before committing any crimes.

Read more: Challenge extremists instead of staying silent

Most people are afraid to contact authorities because they don't have any hard information. But that is exactly the way to stop perpetrators – before they enter the planning phase and become a threat to others.

How similar are such perpetrators to lone-wolf terrorists or those from groups like "Islamic State" (IS)?

Although it has yet to be fully proven empirically, my theory is that individual terrorists and those who run amok are very similar. That is not, however, the case when it comes to perpetrators from terror groups. Most of these are criminals who already have police records. Most have a history of violence or drug abuse and thus have a long list of previous convictions.

Individual perpetrators are different — regardless of whether they are motivated by far-right or Islamic extremism, or a general hostility toward society as a whole. That all has to do with personality or psychological disorders.

Should we fear copycat attacks like those spoken of when it comes to Islamic terror?

We already have them. We have seen an increase in such violent acts since the November 2015 terror attacks in Paris, even here in Germany. They garner different degrees of attention, nevertheless, the discussion that comes out of them is always the same.

But less when it comes to far-right extremism.

And that is exactly the problem! People think in categories. If I tell you that perpetrators are at times interchangeable in terms of their ideology because their motivation has more to do with their own personality than anything else, that means we have far-right attacks at one time and Islamic attacks at another. But there are also those who run amok by driving a truck into a group of people for no clear ideological reason.

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Such people are simply ill and full of hate toward others. They want to attain negative fame with such acts and some are even willing to die to achieve it. We have been facing a growing threat for years.

What role do social media play? Can the so-called echo chamber effect in which a person's views are amplified by other like-minded users trigger or at least facilitate such attacks?

Yes. Most often, individual perpetrators are people with few or no social contacts. So what do they do? They go online and seek out those forums that reinforce their hate and rejection of others or other groups.

We have seen that to an extreme degree among young perpetrators because these often dive into fan scenes that glorify those who carry out mass shootings and the like. We also see it when it comes to IS, where people move among certain Islamist groups in order to further sow hate.

Britta Bannenberg is a professor of criminology at the Justus Liebig University in Giessen, Germany. She has researched individuals who run amok or threaten to do so for years.