Apparently Gary Foster "used his knowledge of bank operations" to get the job done.

Foster, according to the U.S. Attorney’s Office in New York, is being charged with embezzling more than $19 million from Citigroup. He was arrested Sunday morning at JFK Airport when he arrived on a flight from Bangkok, the U.S. Attorney’s Office said in a news release.

According to a court case against him, Foster is charged with transferring money from Citigroup accounts into a cash account and then he wired the money into his personal account at another bank. Foster caused an incorrect contract or deal number to be placed in the wire transfer instructions to hide his activities, the DOJ said.

Let this be a lesson to those considering taking a page from Foster (or brother from another mother Jim Glover)'s playabook- attention to detail counts!

Update: from the complaint:

Mr. Foster, who supervised a derivatives unit, was based in the bank's office tower in Long Island City. He worked in the internal treasury finance department, which funds loans and other business transactions inside Citigroup.

In a series of eight transfers, between July and December 2010, about $900,000 of the money he allegedly took came from the bank's interest expense account, while an additional $14.3 million came from its debt adjustment account, the complaint said. The transactions went unnoticed until a recent audit, a Citigroup investigator told the Federal Bureau of Investigation, the complaint says. In one transfer cited by the authorities, he allegedly wired himself $3.9 million on Nov. 8, 2010. Mr. Foster allegedly put phony contract or deal numbers in the reference lines for his wire transfers to make them look like they were for legitimate contracts.

Former Citigroup Official Arrested for Bank Fraud [Deal Journal]
Former Citi Exec Charged In $19 Million Theft [WSJ]