Gambaryan pursued the fraudsters, executed the warrants, made the arrests, but he began to realize that if he didn’t somehow alter his course, he could easily spend the rest of his career assigned to the IRS equivalent of street crime. These were hardly the white-collar kingpins and international mafia figures he dreamed of taking down. So after a couple of years, he made a commitment to himself: He’d no longer settle for whatever investigations fell to him. He’d make cases of his own.