Luigi Mangione, who has been accused of killing UnitedHealthcare CEO Brian Thompson, has been described as having

expressed interest in more rational, evidence-based forms of compassion, like effective altruism

(source) and

wanted to meet my other founding members and start a community based on ideas like rationalism, Stoicism, and effective altruism

(source, both quoting the same person).

At closing of this market, I will try to use my best judgment to determine if he was actually involved in the effective altruism community in each way prior to his arrest. If there is no evidence of him being involved in some way, that way will resolve NO by default.