Threatening. Male caller left message on our home machine and told us we had to call him back to avoid magistrate or grand jury investigation because of a criminal offense. If we do not call him we could face jail time. He left this number (which matched the caller ID) but did not identify himself or who he [purportedly] worked for.
We have received 2 calls in the last 2 weeks from men with noticeable foreign accents threatening action by the IRS (a warrant for our arrest, the need to appear before a federal magistrate, etc.) unless we called them back at this number and "cooperated." We reported the calls to our local police department and was told that they'd received "thousands" of complaints. The police also told us that the calls couldn't be stopped or traced because they were coming from a telephone number outside the U.S. These crooks apparently also have an app that generates a U.S. phone number and causes the local number to appear on a U.S. caller i.d. Don't call them back or do anything else that might encourage them!