Are you talking about the difference between proximal and ultimate causes? As in the proximal cause of these people dying was an explosion from a bomb set by Kaczynski, while the ultimate cause was that the things that caused Kaczynski's poor mental health that led him to those actions.

Separately I like the phrase "a reason is not an excuse" quite a lot. I can empathise with people who make terrible decisions and understand their reasoning, but that doesn't make me excuse the choices that they made.