If (big if) it turns out that one of the pilots or crew committed an act of murder/suicide, and it wasn't a political act, we need to be very careful about what that means or what we should do about it. Despite the publicity these events generate, mass murder is exceedingly rare.
So far we have avoided putting security inspection into malls, theaters, schools (mostly), and I would hope that common sense can prevail here.
There are usually no conclusions to be drawn in these events. To quote the New Yorker: The problem with generalities about mass murderers is that the sample size is tiny, and most die before they can be examined. Almost half of all mass murderers commit suicide in the act, and many others are killed by police.