Research Summary The lone-actor terrorist population can be extremely heterogenous and difficult to detect. Intelligence is key to countering this threat. This study devises a typology of person-environment interactions which could serve as a framework for intelligence-gathering and risk assessment. We use cluster analysis and a previously-developed Risk Analysis Framework (RAF) to identify relations between three components: propensity, situation and network. The analysis reveals four person-exposure patterns (PEPs): solitary, susceptible, situational and selection.  The solitary PEP lacks common indicators of a propensity to pursue terrorist action. What indicators are present may not manifest until late in the offending process. The susceptible PEP suggests a style of interaction whereby cognitive susceptibility, manifesting as mental illness, is a key factor in the emergence of the propensity/motivation to commit a terrorist attack. This configuration typifies cases where radicalisation may occur in a short time span. The situational PEP demonstrates how situational stressors may act as warnings of acceleration towards violent action; the challenge being to capture evidence of these stressors and their effects. Lastly, the selection PEP demonstrates higher frequencies of leakage and antecedent violent behaviours. These offenders may be known to the community or other agencies, suggesting specific opportunities for detection and disruption.   Policy Implications Our findings have two key policy implications. First, given the multifinality of terrorism risk indicators, we suggest a move towards a structured-professional judgement approach to the risk analysis of lone-actor terrorists. Second, we present the PEP typology as a framework for intelligence-gathering. Existing frameworks predominantly focus on mobilisation indicators. We suggest expanding data collection to include propensity and situational indicators, as operationalised here, and utilising the PEP typology to inform decisions about the emergence of the motivation to commit an attack. To do so, it is necessary to pursue a multiagency approach to intelligence-gathering.