In this paper, I introduce the ethical dilemma due to the disaster of the space shuttle Challenger. I discuss with regard to the circumstance of ethical dilemma how we are able to assess, in terms of the probabilistic theory of causality at the individual level, the causal responsibility of two agents, the engineer and the manager, for the devastating disaster. I introduce four types of causal relevance ('because of', 'despite', 'independent of', 'autonomous of') that are explicated in terms of probability trajectory. I show how we are able to assess and explain the agents' causal responsibilities in terms of the four types of causal relevance. I also show how we are able to explain the agents' causal responsibility in terms of preemption, counterfactual conditionals and contrastive causation in addition to the probability trajectory. Finally, I notice that we need to discuss how causal responsibility is connected to ethical responsibility and legal responsibility both.