Inside the mind of a mass shooter

On Oct 1, according to police, Stephen Paddock opened fire on people attending a country music festival in Las Vegas, Nevada, from an overlooking hotel, killing at least 59 people and injuring more than 500 others. Paddock, a 64-yearold former accountant with no criminal record, was ultimately found in his hotel room, dead, with some 23 guns, including more than 10 assault weapons. Police later found an additional 19 firearms, explosives, and several thousands of rounds of ammunition in Paddock's home. What the authorities have not found, however, is a motive.

More details about Paddock's mindset and objectives will probably come to light in the coming days. But so-called lone wolf mass shooters - individual perpetrators of attacks with no ties to any movement or ideology - are not a new phenomenon in the United States, and previous incidents may offer important clues about the motivations and thought processes of mass shooters such as Paddock.

Most mass shooters do not survive their own attacks; they either kill themselves or let police do the job. But those who have survived have shown some common features, such as narcissistic personality disorder and paranoid schizophrenia being the two most frequent diagnoses. That was the case with Anders Breivik, the Norwegian far-right terrorist who, in 2011, detonated a van bomb that killed eight people, before shooting dead 69 participants in a youth summer camp. He remains in prison in Norway.