In case it isn't obvious - the "let's wait and see" approach is fine when one is dealing with the remnants of an airplane that crashed for reasons that are unknown but presumed to exist. The air accident investigator's job is to pull together what are often very subtle clues to get a first impression of what may have happened, and then work it through to the final conclusion. They do an amazing, often miraculous job at getting to the bottom of things and aviation is infinitely safer because of their work. But this is no such case. It is absolutely clear what happened and there is no need for further investigation, and I would say not much reason to pry into the unfortunate life of the person responsible. Life takes tragic turns. No amount of hand-wringing or brow-mopping is going to get around the fact that psychotics are among us, and door or no door, if one of the crew is determined to crash the plane and kill everyone onboard, he's going to find a way to do it.
My concern is that invasive screening procedures actually have the reverse effect, of concentrating those who are naturally manipulative, while chasing away those normal souls to whom intense, invasive scrutiny is anathema. As much as I love flying and aircraft, I would no have more considered a career as a pilot than I would have one as a trapeze artist.