A security camera picture shows the man police say walked into an HSBC Bank in Prospect Park South on May 21.
Police say he gave the teller a note demanding cash, but he left without any money.
Investigators say he then robbed a bank in Flatbush about five hours later.
The suspect is described as a black male, 25 to 35 years old, standing 6-foot to 6-foot-3 and weighing 240 to 260 pounds, with a goatee.
The suspect was wearing clear plastic gloves during both incidents.
anyone with information in regards to this robbery is asked to call the NYPD's Crime Stoppers hotline at 1-800-577-TIPS.
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