202-684-9919

Didn't answer unknown number. First part of voicemail was cut off, but the rest of the computerized male voice mentioned "a judge or a grand jury for a federal criminal offense" along with "we'd like you to cooperate with us and help us to help you."

You're right, its a scam and its been reported several times under several different phone numbers.

If you had answered the call the scammer would have told you that you have committed a crime.  The police are on the way to arrest you.  You can get out of trouble by paying a large fine directly to them, right this minute, by giving them your credit card or bank account number.  The scammer then spends all of your money, far more than the fine you agreed to pay.

Congratulations on not falling for it.