Funny, but I've been thinking along these lines since the day after the attack. It's too perfectly aimed at the 2nd Amendment to rule out that as the intent. Plus, the timing would have been perfect had Clinton been elected instead of Trump. Too focused of an attack on the 2nd Amendment to be ruled out as such.
Same here... almost immediately had that thought which became a frontrunner, to me, once it was confirmed it wasn't a radical Islamist attack... that this was an anti-Trump, anti-conservative and anti-2A attack. The next level of #Resist. JMO.
And, if we find that the monster obtained all of his semi's and bump-stocks, oh I don't know, say after November 8, 2016, then to me, that would be sufficient proof.
And, not to re-ignite the "debate", but the sheer number of conservative/patriotic country music artists and the number of patriotic songs that they produce for their fans, and the success of those songs and artists, reinforces for me the perception that the majority of country artists and fans are pro-America, pro-military, pro-gun, patriotic and conservative.
This is just my opinion and you don't have to believe me, but I would suggest that you ask the Dixie Chicks...