There was snow above 10,000 foot elevation, with two feet remaining on Monarch Crest. The Morphew home is about 8830 ft elevation.
For perspective, Google Earth actually has "street view" from the runs of Monarch Mountain ski area, which allow a fantastic view of what the canyon is like. I dropped the little street view guy down at:
38°30'34.07"N, 106°20'16.01"W
which is 11,198 ft elevation. The views were taken in January 2011. In the background directly above the forward skier, the is a white line tracing up the mountain side, disappearing behind trees and faintly reappearing at the crest. I believe that is the power line cut (lower Colorado Trail) that AM described walking in his search with the neighbor. Where that line disappears, seeming to be about halfway up the mountainside, is actually about the 10,000 foot level. Monarch Crest, above it, averages 11,400 ft.
So back to your question: I stated in another thread that I actually made my living on the business end of a shovel for a while in Colorado Springs, digging all through the winter, and never saw the ground frozen. It is awfully hard, though. Personally, I think that the very minimum tool required would be a Bobcat with one of the higher end backhoe attachments (which can cost as much as a new compact car and has very little use in landscaping). The question becomes:
1. Did BM even own a premium backhoe attachment for his Bobcat?
2. BM would not likely have used a backhoe attachment at the beach job or in Denver. He could have transported his Bobcat on that trailer with a backhoe attachment installed, but it would have been impossible to carry the Bobcat and the backhoe attachment separately, on the same trailer. Did he have time to change one twice, and where was the attachment parked when not on the Bobcat?
One final thought: Using a Bobcat to dig a deep grave is a dangerous operation. The deeply extended bucket and arms exert huge balancing counterweight on the machine, putting it in danger of tipping forward as the arm is curling the bucket to lift the dirt or rock. The resulting tip can plow the operator face first into the earth on the opposite side of the hole. I'm certainly not saying that it can't be done, but where would a landscaper learn to do that?
IMO
The "photo" is a Google Earth screen shot, produced entirely in Google Earth Pro with no external editing.