The timing is suspicious but that doesn't mean it wasn't suicide. If he was determined to kill himself there might be several reasons to do it today. Maybe he wanted to cast suspicion on Boeing. Or maybe he didn't want to testify - could be tons of reasons for that. I have no idea. Just saying the two events could be connected without it being murder.
What he already disclosed has done far more harm than that.
And what he could have said would certainly cause even more harm than his silence.