The package came a day after an unidentified man on a bicycle detonated a crude bomb at the post, but police do not believe the letter and photo are related to the attack, according to the New York Post.
In a statement, Ackerman said the 10-page letter and picture were sent to U.S. Capitol Police and that the package was mailed from a California address.
It was unclear what was said in the letter, but the Post, citing law enforcement officials, said "We did it" referred to the Democratic takeover of Congress in 2006.
Ackerman spokesman Jordan Goldes said the congressman's office did not know the contents of the letter because staffers immediately handed it over to the police.
The Post said the package was mailed to the offices of about a dozen Democratic congressional lawmakers.
©2008 Community News Group
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