who are these people?

They are Indian phone terrorists.

See: http://www.irs.gov/uac/Don%E2%80%99t-be-Scammed-by-Fake-IRS-Communications

Tell them to go to hell if they call you again.

Had a call from Kevin Smith from the Tax Crime Investigating Unit of the IRS. Said there was an arrest warrant against us and our property (?). Clearly a scam, but also clearly very alarming. Since it was a 202 number (I live well west of there) I am very suspicious. I will be reporting this one to the IRS itself.

The call was an Automated voice message from "Melvin Decker" saying that there have been some allegations against me for tax evasion and the message urged us to call the number to avoid arrest and prosecution...  We googled IRS scams and read about similar calls...