Are you suggesting that David and Jack were in fact attacked by some animal and that the officialdom of East Proctor has conspired to keep it a secret?
10 seconds sound clip from the An American Werewolf in London movie soundboard.
You can hear this line at 00:23:45 in the Blu-ray version of the movie.
Quote context
[...]
- I'm sorry if I conflict with your report, Inspector, but Jack and I were not attacked by a man!
- He may have a point, sir. Two strong boys would be able to defend themselves against one man.
- We have an autopsy report on the murderer, who was shot in the act by the local police.
- We have two witnesses to the crime.
- Inspector, the boy seems all right to me, and...
- And I don't rightly know, sir.
[...]