Death by Helmet????

[Nubsnstubs]

Hi folks, back in 1970, my brother, SF officer, 1st Lt. Walter Lee Marcantel was killed in a routine jump at Fort Devens, Mass, 59 days after his tour in VN. He was one of the officers on the mission that Jerry Shriver went MIA.
The verbal report of what transpired was the jump was made from a Beaver aircraft. I don't know how many others were involved in the jump, but my brother was the last to exit the plane. The only other people in the plane was the jump master, and the pilot. I didn't hear anything about a co pilot.
He was preparing to exit . He supposedly was on his butt because of the small door that was the exit point.The story is his reserve chute opened, and was instantly dragged out of the aircraft at what ever speed the craft needs to stay aloft. His head hit the doorway, his helmet strap cut his throat, and since it was a static line jump, as he exited the plane, he had a "Mae West" type of descent. I was told he was dead before he touched the ground.
Ground personel at the scene supposedly caught his body before it touched down. In other words, his jump was noticed from the ground that there was something terrible wrong and got to his landing area to render assistance immediately. I commend the ground personel on their concern about the situation.
Now, my question is this.. Is it possible for the jump helmet chin strap to possibly actually cut someones throat without releasing like the chin straps used on the steel pots the regular GI's used in that time period?
I was in Combat Engineers, and my pot had a quick release ball and claw type attachment. Rarely would it stay attached while running. I have never seen a jump helmet up close and do know if it uses a different locking attachment than the regular pots.
This question has been bothering me for a long time..
Thanks for anyone answering my question..
It would help me if anyone is still around that might have seen this incident, or if someone actually knew and served with Walt.... Jerry Marcantel (in Tucson)