Three masked gunmen stormed a community bank Tuesday, killing one person and wounding two others during an exchange of gunfire with a security guard before fleeing with an undetermined amount of money, authorities said.

The Cook County Medical Examiner's office said the person who died was a man in his 20s.

Earlier, Maria Maher, chief of detectives for the Chicago Police Department, said the victims included a 23-year-old male teller who was shot in the back, a 73-year-old female customer, a 48-year-old male security guard who was shot in the chest.

The suspects were only in the bank for four or five minutes and got away with a small amount of cash, Deputy Police Chief Michael Shields said. He said police were checking the license plate of a vehicle caught on surveillance tape leaving the area.

"Due to the extreme amount of violence in this crime," the FBI is offering a $50,000 reward for their arrests, FBI spokesman Frank Botche said. He said authorities believe the same suspects may have been involved in another bank robbery two weeks earlier.

The suspects entered the Illinois Service Federal Savings and Loan around 9 a.m., grabbed a weapon from one of the bank's two guards, and one suspect jumped over the counter, Shields said.

The bank has no bulletproof separation between customers and tellers, said Chicago Alderman Freddrenna Lyle, a customer of the bank in her ward. She said the bank was trying to appear less intimidating to customers in the largely black community.

Pilar Jones said her daughter, Jasmine Tate, is a teller at the bank and called her from the building. It was her second day on the job.

"She yelled into the phone: 'We're being robbed. A security guard has been shot and I can't get out,"' Jones said. Tate, 18, was unhurt, her mother said.

A recorded message left on the bank's main telephone number Tuesday morning instructed callers to try back later and a voicemail was not immediately returned. Several messages left for comment at the bank's other Chicago branch were not immediately returned.