The past year has seen a global upsurge of violent attacks by lone, mentally unstable individuals. The motivations for these attacks have varied and extremist ideological drivers are rarely ‘pure’, but mental health problems and personal grievances are common themes. Mentally ill and disenfranchised individuals may be vulnerable to extremist messages and propaganda because such beliefs can be a means of interpreting their social difficulties. Terrorist messages can also be adopted by psychotic people who are seeking to make sense of their symptoms. Most lone-actor attacks are preventable, if there is a system in place for identifying and intervening with antecedent behaviours, which include mental disturbances and the social problems that frequently accompany these conditions. Joint police-mental health models developed to assess and manage fixated persons can be applied to other forms of grievance-fuelled, lone-actor violence. This paper describes the establishment of such a service in Australia, and provides some preliminary data. It also discusses the role of mental health in the current security environment.