The Christchurch terror attack in March 2019 was a pivotal incident in the recent history of right-wing terrorism. Utilizing eight proximal warning behaviors from the Terrorist Radicalization Assessment Protocol (TRAP-18), this article provides a qualitative analysis of the attacker’s behavior following the formation of his terrorist intent. Events and activities were coded against the eight warning behaviors and assigned a date where known, thereby creating a comprehensive chronology of events commencing from January 2017 up to the time of the attack. Five insights of theoretical and operational relevance when utilizing proximal warning factors emerge from the analysis: timing; the impact of security awareness; the interplay between factors; the effect of image management; and the social connectedness of lone actors. This study adds to the growing body of empirical evidence supporting the efficacy of the TRAP-18 as an instrument through which to analyze the behavior and mindset of lone actor terrorists. It provides further insights to inform the process of person of interest prioritization among counter-terrorism investigators and contributes to academic knowledge of threat assessment.