Where did this "new evidence" that as many as 13 shots may have been fired come from?
I don't know about you, but I have trouble keeping track of more than about five rapid-fire shots if I'm not prepared for them.
Then there are echoes and stuff and possible return fire not accounted for.
I had a nine-shot .22 revolver. H&R, I believe. Wouldn't shoot worth a darn. Sorta like all 9 tolerances added up in it or something.