I went back and forth in my head as I watched it. First I thought it was a bad idea for the safety. But then they got a really good free kick, and Brentsville had not been able to move the ball at all in the second half, so I understood the decision. But then Brentsville was able to move the ball, slowly but surely to just make it in the last seconds.
If you really want to be critical, I would say why didn't Armstrong just run the ball every snap of that possession and force time off the clock or Brentsville to use timeouts, and then you still have the punt/safety decision to make, but from a more advantageous clock position.
But when it comes down to it, Brentsville played well without their starting qb, and Armstrong played well without their coach. And while Brentsville did get a lot of crucial calls from the refs, I can't criticize the refs when my view is from a single NFHS camera.