This is an interview with someone presented as some type of expert that obviously is not an expert. 1) it is not hard to get a silencer. You can make one in under an hour with cheap parts from a hardware store and a drill. 2) the CEO was at a conference. It's not surprising that this person "knew he would be there", it's interesting that this interviewee stresses this point like it is some big one to be made. The CEO…
But if I have to speculate (who doesn't love that) - could have been a disgruntled veteran. Most of them have some serious health issues, and imagining situation where he isn't treated anymore but feels he should have been isn't that hard for such bad public healthcare system as US has. Or hardcore NRA member with same motivation. On youtube some gunsmith videos go up to (tens of) millions of views.