Nothing unusal about that. I was an attorney for the IRS. People get crazy over taxes. I once had a guy tell the judge in chambers that he couldn't be taxed because he was an "ambassador of yahweh." Given that over 3 dozen illegal weapons had been sized from his home when it was raided, the Judge was justifiably concerned about that nut's incoherent ramblings and called in the marshals to restrain him. They found 2 hadnguns on him.
A few months later another nut case in Seattle pulled a revolver from his brief case durng a tax court trail, said "judge, if you are going to take my money you might as well take my life with it" then stuck the gun in his mouth and blew his own brains out.
A few years before all that a nut case shot and killed a well respected revenue officer in Buffalo, NY - the federal courtbouse was renamed fter the revenue officer.
IRS CI agents are law enforcement. Same as FBI, DEA and Secret Service.