Just the usual 'expert' on tv, folks on the Internet with BS explanations. So this person was trans. We've had White guys shooting up black churches, Black guys shooting up white police, white guys shooting up Sikhs, Antiabortion guys shooting abortion docs in church, Christians shooting up Jewish places of worship, Liberals shooting up Conservative ball games, Asian shooters - so every demographic is causal? Only if you don't like that demographic it seems.
As HCM said, the best we have is that a grievance of some type seems to lead to planning and the event. Add that to suicide in some as I mentioned as some kind of demonstration related to the grievance. In the case, the buying of guns in a manner not related to a real interest may be a red flag. However, we've had shooters who go to the range to actually practice their rampage.