There was a rather extensive article in the Inland valley News that went into greater depth with this mining venture.
Apparently, the were two illegal Mexican laborers, one on top unloading buckets and another on the bottom shoveling and filling the buckets.
As there was no air at the 60' level, and the laborer was breathing thru a garden hose
The soil in that area is alluvial sand and is subject to caving when the moisture content is minimalized.
A miss-step could easily have caused a cave-in burying this miner-of-sorts.
Not only do we have an owner who as I said "was not the brightest bulb on the tree", but we also have two illegal nationals that are equally as dim

...(dimwitted).
On the brighter side, all of these sands do contain a marginal amount of gold fines, but not enough to recover, even at today's gold prices.
Besides, the mine in question was in a urban neighborhood with the typical 20' setback from the street right-of-way. The article also included a published picture showing a mound of dirt that was as high as the single-story residence.
I do feel that this person is a good candidate for the "Darwin Award".