An interesting scenario - concussion

[pmulcahy11b]

I was recently reading in a book about Cobra gunships in Vietnam. One crew was trying to stop a PT-76, but had no weapons that could penetrate the PT-76's armor. They decided to try to make it turn tail by hammering it with HE rockets, and their fire was very accurate.

Then the PT-76 just coasted to a stop. When the infantry guys got to it and got the hatches open, the crew was dead, but the PT-76 was essentially undamaged. The concussion from the HE rockets had gone through the armor and killed the crew.

Can anyone think of a rule for that?