A man stole an estimated $28 million worth of diamonds from an ABN-AMRO bank in Antwerp, Belgium.

Police believe the man carefully planned the robbery, reports say, charming bank employees and becoming one of few customers to get access to the ultra-secure bank area. The man gave the name Carlos Hector Flomenbaum from Argentina—likely a false identity, since a passport with that name was stolen in Israel.

The man is described as gray-haired, 6 feet 3 inches tall, and between the ages of 55 and 60. He has an American accent and often wears a baseball cap.