In New Vegas the Brotherhood of Steel was destroyed, how?!?

I wanted to join the Brotherhood of Steel, so I did the mission. Then I did the mission to take the elder away, since he gave someone else orders without permission. Then he said to wait a couple of days to talk to him again. I waited a day, then I whent to do something, then waited another day. By this it's probably been 2 1/2 days in game. Then I go to the hideout and I walk in. Suddenly this NCR ranger which I talked him into leaving the first time I had my explosive collar on. Suddenly walks out from the inside. I walk into the main thing and my arm and leg are crippled in an explosive. I hear nothing on the intercom. I pick the lock from the broken door and I open it. It's caved in. WHAT HAPPENED?!?!