‘They’re not wolves – they’re sheep’: the psychiatrist who spent decades meeting and studying lone-actor mass killers

Paul E Mullen’s new book, Running Amok, examines the patterns and cultural scripts behind the actions of lone mass killers – and how they can be prevented. Photograph: Ellen Smith/The Guardian

Dr Paul E Mullen and his family were living near Dunedin, New Zealand when, one evening in November 1990, they heard gunfire. The shots continued into the night, followed by the distant sound of police and ambulances. At 9pm, a hospital colleague told him that a few kilometres away, in Aramoana, someone with a gun had started shooting.

As it turned out, Mullen had heard of the perpetrator before; one of his long-term patients was the man’s nextdoor neighbour, and soon Mullen would learn that many other people he knew had been injured or killed.