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.
suicidal people are, be definition, crazy. It's impossible to put yourself in their shoes. When the switch flips, suicide just seems like the logical solution and is very matter-of-fact. It's impossible to really understand what's going on in a suicidal person's mind at the time.