Stop believing them when they tell you why it happened.
You've learned not to believe them in most other instances. You've learned they're just selling stuff. So why in the world would you believe them when they tell you why it happened? When they present to you, like Colin Powell at the U.N., purported interviews with people who knew, histories of social networking, and prior odd behaviors...when they detail these things to you, what makes you think this is the one situation in which they're being honest and complete?
Stop believing anything they say. Even if it seems to vindicate you or confirm your suspicions. In any instance, no matter how horrifying or mundane, stop listening to them. Stop analyzing what they do and what they included and what they omitted, because they are several steps ahead of you and have already planned what to include and what to omit because they know what you will conclude based on their inflection and their omission. It is a rigged game, like war, at which you can only win by not playing. This may shock you, but they are smarter than you, and the manner in which you heard about it was preplanned, part of the setup, just like the Santa Claus suit on the Salvation Army guy. The sheeple may fall for the dinging bell, and maybe you're clever enough to ignore even the mission statement on the organization's website, but you're already at the store, aren't you? Whoops--you lose. Like a cheating mystery author, they've planned the red herring, the double red herring, and everything else you think you're so clever at identifying. It's not even about who did it. It's about you having already bought the book before you even began "dissecting" and "analyzing" it. You lose.
They are liars. They are salesmen. Everything they do is misdirection, deception, bullying, coaxing, selling, flattering, lying, lying, they have lost your trust a thousand times over. So stop believing them when they tell you why it happened.