Salute!
TNX for "knowledgeable" posts, Wolf and Spaz.
The "eye witness" sighting indicates a low level nav mission. And one report from a local news outfit or sheriff stated wreckage was along a half mile of a road. So CFIT is not outta the question.
I wouldn't rule out the oxygen problem, as down real low and fast only one second of a problem can be fatal, as we know from our own personal experiences. Although there won't be much to analyze, toxicology is very advanced these days, and even back in the 80's we could tell lots about our departed buddies' physical state upon impact.
RIP
Gums sends...