“the tail gunner was dead”
If I remember correctly, the B-17 did not have a tail gun until much later in the war.
I believe it was the chin turret in the front that was added later. Like around the F model? German fighters had found attacking head on was the best approach.
The B-17E introduced the tail gun. It was the first production run to go over 42 units— to 512— and first flew on September 5, 1941 (over three months before the US entry into the war).
http://en.wikipedia.org/wiki/B-17
If I remember right, those B-17s which arrived at Pearl Harbor during the attack did not have tail gunners.
I think every picture or video of them in Europe showed them having tail guns which were very much needed. They eventually added a chin turret too.
The B-17 had a tail-gunner position from 1941 to ‘45.