What drives someone to commit the unthinkable? In Running Amok, forensic psychiatrist Paul E. Mullen burrows into the minds of mass murderers to learn how and why they become spectres haunting modern communities. Drawing on decades of experience assessing killers such as the perpetrator of the 1996 Port Arthur massacre in Australia, Mullen examines the key forces that unite them: obsessive rage, personal grievance, fascination with weapons and a quest for infamy often culminating in suicide. Mullen reveals these killers not as incomprehensible monsters, but as deeply disturbed individuals shaped by knowable forces. Crucially, he offers guidance on recognising warning signs and improving threat assessment. He also explores the corrosive role of media sensationalism, which fuels grandiose fantasies and inspires copycat violence.