I was an M203 grenadier and can say that it could easily have happened that way. Those rounds arm themselves at a short distance out of the tube, and the contents can injure the grenadier. IIRC, the old M79 worked about the same way.
Here's some brainless, opinionated puffings by Snopes about the Ron Brown Crash:
"What "new evidence"? Ron Brown and 34 others were killed in a plane crash in Croatia on 3 April 1996. The plane slammed into a mountain while on landing approach. There were no survivors.
A lot has been made of an x-ray of Brown's skull in which what looks like a round entry wound appears. Closer examination of Brown's skull by military officials revealed no bullet, no bone fragments, no metal fragments and, even more telling, no exit wound.
Simply imagining a scenario under which Ron Brown could have been shot takes one into the realm of the absurd. Was he shot in the head during the flight, in full view of thirty-four other witnesses? (If so, how did they get off the plane?) Did the killers shoot him before the flight, then bundle his body into a seat (just like "Weekend at Bernie's") and hope nobody noticed the gaping hole in his head? Or did Croatian commandos fortuitously appear on the scene to scale a mountain and pump a bullet into the head of an already-dead plane crash victim?
See what the Air Force had to say about this crash."
[link to the Air Force Clinton-imposed propaganda sheet]
I heard what four forensics specialists had to say about those photos and x-rays, and it makes sense to a radiology technician I talked to, who also was concerned about the metal fragments seen in Brown's scalp. To ignore all that evidence is hogwash. To think that Croatian insurgents might not have been hiding in that area is hogwash. To ignore the report that a light beacon was moved, and that the operative at the airport might be armed is also hogwash. The man in charge of the light beacon allegedly shot himself a few weeks later. Just a coincidence, right? The crash took place on April 3, the plane crashing into a mountain on the same date of Martain Luther King's 'made it to the mountaintop' speech. Just a coincidence, right?
Snopes should be called 'dopes.com'.