Glad you were there and knew what was going on. Two of the most important things to consider when in or near the trees; slow down! Most tree well accidents start from a high speed tomahawk into them. Second use good protocols; it's not enough to just ride with a partner. You need to be leapfrogging the run so you are actually watching each other at all times.
If you haven't done so yet, click here and read this online information from th US Forest Service about NARSID ( non avalanche related snow immersion death) and tree wells:
Thanks for putting up the links. Have posted this one on facebook Tree Well and Snow Immersion Suffocation (SIS) Information :: Home
Even more crazy is how spaced out the trees at Hemlock are. You can see in the pic above for an idea. When going fast though, you don't know where you'll end up.
I had two bad tomahawks from flat light and hitting ditches/drops without seeing them, and my gf had a bad incident hitting a cat track at full tilt where we couldn't find one of her skis for a few minutes and had to climb around in waist deep pow.
Shit, it's so fun but my respect levels for deep snow have been bumped right up there!