As best as I can tell, it looks like someone took a little ride today.  We may hear more later but from my perspective I saw two tracks above the avalanche leading into it, one track down the debris to an area where it looks like a second person was collecting himself and perhaps some of his gear, then two tracks down the rest of the debris and out.

It didn't look like a real impressive slide from a distance.

When I got up to the crown face, I was more impressed.  It was close to 20" at the deepest spot.  A portion of it had broken through last weeks sun crust and ran on facets above the rain crust.  It was a very wind loaded pocket with a foot or more snow drifted in.

The column failed on isolation when I was testing the crown face.

The starting zone I measured at 45 degrees.  Very steep.  This no doubt played a big role.

Facets were no doubt what failed.  The first photo below are facets from the part that broke through last weeks sun crust.  These were sandwiched between the rain crust and the sun crust.

The second photo is from the portion of the avalanche that broke above the sun crust which also had facets.  No wonder they're nicknamed "squares".