An update today re the burning shed pointed to "The Twelve Tribes" as the origin.
I'd post the article but it is on the Denvr Post so it is not allowed here.
The title is "Boulder County investigators narrow Marshall fire’s origin to single neighborhood"
The address reported in the article is near the intersection (93 and 170): 5325 Eldorado Springs Dr
That’s not a group I had heard of before. They actually sound pretty tame for Boulder. I hope they find out how this started