Sounds more like someone with access to personal information pretending to the the IRS trying to scam or troll him. (Some one from a Leftist organization.)
He should contact the IRS at some number other than the one given by the "Agent" and verify that the "agent" actually works for the IRS and actually made a visit.
Note that the IRS acknowledged the “visit” and gave a version of an explanation. So this was apparently real.