Well, again I'm glad you made it back safely, seriously. I don't want to be preachy, because there's plenty of that on this web site, and that's not my interests, but you are luckier than you probably know.
You remember the avalanche debris you came to at the bottom of Leuthold Couloir? That avalanche occurred around 4:30 p.m. Thursday afternoon and slides continued into the early evening. The one that came down through Leuthold was the largest one. Why do I know this? I have a good view of the mountain from my house, a pair of good binoculars, and climbed the route (the standard Leuthold route) a few hours earlier than you did.
Anyway that avalanche you witness from Castle Crags on your way back was tiny compared to the one that came off Reid Headwall at 11:25 a.m. (give or take a couple minutes, I actually saw it happen with the binoc's from my house). This avalanche was at least twice as big as the debris pile you saw at the base of Leuthold and ran out on the Reid Glacier twice as far. Obviously this would have covered the boot path area about where your brother was in the last photo (give or take).
Again, I'm not telling you this to be preachy, or to be "more awesome" than someone else, I'll leave that to other bloggers. I'm not "more awesome" than anyone- I still have sore calves because we hauled ass until we got well past the hourglass and I'm out of climbing shape. It just pertains to what we were both doing that day. Your pictures are way better than ours.