Rider triggered Avalanche, 1 partially buried

From email: "One of my crew was partially buried in an avalanche today(head about 1’ down, leg and arm still above snow) at approximately 13:10 hrs.  Slope was greater than 35 degrees, crown approximately 85 yards wide, over 3’ at its thickest point.  I believe it was a NE exposure with wind loading at the top.  I had a bad feeling about this slope and mentioned it to my crew and avoided riding on it until one rider ran out of gas and I had to help him.  Upon completion of task, I rode back to a spot that wasn’t as safe a vantage point as what I had previously stayed at, but the intention was we were all on our way out.  So I parked and within 30 seconds, I hear my friend yelling behind me. I turn and immediately think “oh he’s about to hit us”.  So, I  attempted to start up my sled, to no avail While watching behind me.  Suddenly, a massive “snow cloud” appeared about 30 yards above him and it took about 2-4 seconds to register that it was an avalanche and not another rider careening out of control at us.  By that time, it was too late to do anything.  The avalanche had reached the back of my friend and my sled, pushing us forward about 6 feet at 3-4mph.  After it stopped, I assessed 3 of four of our team was accounted for, and one (the one who yelled at us) was not.  He was partially buried by the front of the avalanche much like our sleds were.  Fortunately, within 5 seconds, I saw an arm and a leg sticking out of the snow and we had his airway and head cleared within about 20 seconds.   He was located approximately 10 yards from us.  "