And throw in the fact that lying to a Federal agent can lead to felony charges, the behavior of his interrogators is very typical.
My favourite was a CBP asking me "what do you do for work" (lovely unspecific question, that) then pretending to get upset with me for not telling him I was unemployed at the moment. I resisted telling him I personally don't consider unemployment a career...
"You told the border guard you're entering the country to work." "What? No! I never said that! I'm entering to marry my fiancé!"
"I'm here because of the MBA conference." "NBA? We didn't know there was a basketball event in this building."
Yeah, I've seen it a number of times.
They weren't upset. They were manipulating the author. They weren't stupid. They already had agents heading to the apartment to investigate.