My wife just got a threatening call on her cell phone from this number (i.e., 202-506-9654). The recorded message said the call was from the IRS and legal action would take place if she did not respond. The call ended with "Good bye and take care," which certainly identifies it as a scam because the IRS would never end a call in this manner.
We received same threatening call from same number and from same person 6/24/14. It sounded like a robo call and not very professional. It came to our Calif number and ended with same "Good bye and take care".