Agreed that people can express multiple emotions rapidly after deaths, and some people exhibit opposite reactions to situations as part of their particular personality (i.e.: the brother). i also find his demeanor odd. There is no doubt a laugh happening as the clip starts- its immediately stifled. and after multiple views see no signs of sorrow, only the 'holding back' and strange eye movements but no wetness at all in eye rim- yes, i looked very closely. nothing however can be proven from 'odd behavior'. more concerning- whoever wrote the bottom part about the girlfriend... this doc is second hand and very weak... it blatantly states SHE "figured it out" by looking for a friend and thinks seth 'must have' also found out. that is nothing more than a guess. the father mentions the polling interest which seems suspect at first- but if mr. rich did in fact develop the dnc polling app, this would make sense as to what the father is referring to... if it was something more sinister, why would he have just SAID it out loud!?? esp when they appear to be rehearsed and the dad cutting off the mom earlier, but then he spills the beans? i find their 'we may never know' the most troubling... and other ways of speech ( yes very much like SH). in this scenario and in viewing this interview, pizzagate findings make the picture make more sense... the family is being hush hush, diverting fact that ?flash drive was stolen by repeating no robbery...he could be under protection or is dead and secret investigation occurring----- f/u interview with the brother would give another chance to see his personality on display and look for signs of sorrow/etc.