Interesting story. I would have thought it physically impossible to open the door at that flight level.
This looks like the flight it happened on: BE20 CGBYN
Canadian registry is here.
The KingAir door is not a ‘plug’ type, it simply opens outward and downward.
I’m surprised it wasn’t ripped off at that speed.
KA MED’s are very robust, the hinge is very strong and between the gas strut door let-down and the hand-grab/support cable, I not too surprised…
I’ll tell you what though, I’m not going flying with Mr. Alldridge…he sure doesn’t seem to understand the airplane very well for having “logged thousands of hours in King Air 200 aircraft”. 
Not sure if the accident A/C was a 200 or 200C model… but since it appears they used it for medivac work it’s probably a C and has the upward swinging cargo door for stretchers, etc. I’ve never dealt with a cargo door on a King Air but I recall from training that it uses a different seal system than the regular airstair version. I don’t think it uses the typical latch release button that has a pressure differential safety, and also has no bleed air door seal system. At least for the cargo door portion. Might be pretty simple for a PAX to pop the whole dang door open in flight?
Looking up the aircraft in the Canadian Aircraft Registry (see link in my post above), I found:
Common Name: Beech Type Certified Model B200
Serial No: BB 1232
Type Certificate - CAR Standard
Right, “common name” is model B200… the B200C is just a variant of that model.
Just not sure how a PAX could overcome the pressurization safety mechanism on the latch release button for the airstair PLUS the positively inflated door seal on a normal B200. Doesn’t make sense. 
Edit: Just found this… she doesn’t have a cargo door:
The following is an hypothesis! The pilots depressurized the aircraft and went on oxygen in an attempt to render the unruly passenger unconscious.
Can’t see a single individual overcoming the door safeties while the aircraft was pressurized. The load on the locking pins is measured in tons.
Okay…now I’m gonna have to get out my B200 books, as it’s been over 6 years since I’ve flown one.
Phantomjet…the C model has a door within a door set-up. Like this one. You can see the outline of the larger cargo door.
http://www.controller.com/images/Controller/fullsize/78811439.jpg
It does not appear from the photo phantomjet posted that the subject aircraft has the cargo door. Look at the separation between the last two windows before the door in both photos, much more space between them in the plane with the cargo door. Also the next to last window is smaller in the cargo door and matches the last window in size.
No no…that’s correct, the subject aircraft was not a C model. I was just showing phantomjet what the cargo door setup looked like. 
Now that I’ve refreshed my memory… The following in italics is paraphrased from the AFM.
The B200 door has two latch bolts on each side of the door and two latch hooks at the top of the door that roll over two pins at the top of the door frame. Unlocking the door from the inside is a two hand operation. It requires that a release button be depressed prior to the handle being rotated with the other hand. The release button acts as a saftey device to prevent the accidental opening of the door. In-flight, as an additional safety measure, a differential-pressure-sensitive diaphram is incorporated into the release-button mechanism. The outboard side of the diaphram is open to atmospheric pressure and the inboard side to cabin pressure. As the differential pressure increases, it becomes more difficult to depress the release button as the diaphram move against it.
Now, the maximum differential pressure of the B200’s pressurization system is about 6.5 psi, so while very difficult…it would not be impossible to depress the release button, rotate the handle, and open the door in-flight.
…and how many passengers did you lose?
Only the ones that deserved it… http://www.websmileys.com/sm/evil/105.gif
I am Italian after all…
Yup, I understand the door set-up… My theory was that the PAX failed opening the airstair and maybe spotted the latches for the entire cargo door and had success since there’s no pressure safeties on it. (IIRC you just pull 2 access panels in the cabin and turn the levers) My manual went in the basement 10 years ago, and again I never dealt with the cargo door set-up, just was threatened to fly one at one point in my career. 
Also, it’s easy to spot a 200C since they have 2 small aft windows instead of the normal 1.
Pretty much… The BIG door has eight latches. One handle actuates two on each side of the door, and the other handle actuates four latch hooks across the bottom.
thought you couldnt open that thing in midair?
phantom pax!!!