The Cessna 421 Gulf Crash: Pressurization Problem? (Speculation)

Flightaware flight track of a Cessna 421
Source: Flight Tracking Information

A twin engine Cessna crashed earlier today in the Gulf of Mexico after circling for a couple of hours.  It definitely seemed uncontrolled based on the flight track.  I would assume the autopilot was still engaged to keep it at altitude, but then why would it have circled for so long?  I have a theory already. At left is the actual flight track from

Certainly the full details of what happened won’t be known for some time, but one of the local news stations in Florida said that two F-15’s were scrambled to check out the planeafter the pilot didn’t respond to radio calls.  They also reported that the plane was intercepted at 28,000ft.

Cessna 421 from Wikipedia
Cessna 421 Similar to The One That Crashed In the Gulf Today

I wasn’t immediately familiar with the plane type, a Cessna 421, so I was surprised to hear in initial reports that it was a Cessna at FL 280 (and not specifically a Citation) flying that high.  So I did some quick research and found that the plane in question is certainly capable of that altitude.  The 421 is apparently a variant of the Cessna 411, which I had heard of, but the main difference between the two planes is that the 421 is pressurized.  So, that answered that question.  The next question is, of course, what happened?

Payne Stewart Similarity?

Payne Stewarts Learjet 35 That Crashed (Source: Wikipedia)
Payne Stewarts Fated Lear 35

The F-15’s that chased the fated 421, reported that the cockpit windows appeared to be iced over.  That situation is reminiscent of the Learjet crash that killed golfer Payne Stewart in 1999. In that incident, the plane was a Learjet 35 en-route to Dallas from Orlando.  When it missed its turn and went out of radio communication, the Air Force also intercepted that plane, but at 46k ft.  Those intercept pilots also reported that the cockpit windows had seemed iced over.  The plane eventually crashed in South Dakota, and the cause was ruled as pilot hypoxia from loss of cabin pressure.

Pure Speculation

Of course this incident just happened today, so there are few details, but loss of cabin pressure at altitude seems plausible.  If that happened, and the pilot slowly lost consciousness (assuming it was a gradual pressure loss), then how come the plane didn’t continue to fly straight until it ran out of fuel, as the Learjet did above?  If the pilot had fallen on the controls forcefully enough, wouldn’t the autopilot have disengaged?  Perhaps his foot was on the rudder, and that didn’t disengage the AP?  I’m sure the questions will be answered eventually.