Still lots of unknowns and different points of views from articles. I'll save final judgement until a full report comes out but as a whole... it's better to be overly cautious these days. I think any final report will show that this was an over-reaction, everyone is on edge all the time these days... but you often hear survivors or witnesses after the fact talking about how something felt wrong, the person(s) were giving off bad vibes, acting oddly, etc... and no one intervened.
Maybe the FA/GA had a really strong sense of that? Plus one article says they tried to flee from the employee?