FBI 164-81, Vault Part 16 p. 406 (DB Cooper-4784), Letter, serial SE 164-81-1381 (as read from the transcript) — cooper.theunsolved.net/parts/Cooper-Part-16/pages/406
The scan is the source; the transcript is machine-generated from it.
Dear Editor:
To the Public:
I must ask you, who in the hell do some of you people think you
are, and what in the hell do you think you're doing.
I have suceeded in pulling off one of the most successful, talked
about crimes of today. Then some guy credits himself with the masterpiece
and thanks everbody, for their cooperation an hospitality...Well Damn it,
this is making me look very stupid. These prank letters must stop...
No one was indangered, the caper was only committed to show the
unbelieving world that a PERFECT crime was possible.
I have notified the F.B.I. asking that they grant me Amnesty.
The money will be returned.