I was watching live, it was like he saw something, then heard something..I wonder if he could see out to the street from his 'command center'. He came back looking like a man who had his house shot at - so I think any questions of this being real are not at all appropriate - he's got a family in there.
It really wouldn't shock me that its some deranged person who wants to be a streamer but failed at it, and its just their way of being famous - but that could be a crazy theory. (it could be a case of wrong house targeted too - many years ago my family's car kept getting windows broken because my neighbor yelled at some kids - and at that moment our car was in front of their house, so they assumed it was hers)
I'd have my family out of there today until they catch that person, he's fortunate to have the funds to do that without going broke. Gated communities where he lives (SoCal) are so expensive though, might not be an option even for a guy making 100K a month+
Anyway, hope they are all safe.