Chicago ? Teller Allan Tooles was in the middle of cashing a customer’s check when three masked men stormed into the South Side bank Tuesday, screaming words he couldn’t make out.

One of the robbers leaped over the counter and forced co-worker Tramaine Gibson at gunpoint to the vault, but Gibson didn’t have the combination, Tooles believes. Gibson, who had worked at the Illinois Service Federal Savings and Loan branch for six months, was then shot.

Gibson, 23, a married father of two, died later at Mt. Sinai Hospital. A customer and a security guard also were wounded. The FBI and Chicago police launched a manhunt for the three bandits, who escaped after the brazen morning holdup, one of Chicago’s most violent in many years, authorities said.

The robbery was over in about five minutes. The three men escaped in a maroon Oldsmobile with only a small amount of cash, police said.

Two nearby schools were temporarily put on lockdown while police searched the area.

Later Tuesday, police found what they believe to be the getaway car abandoned at 66th Street and Wabash Avenue.

The FBI is offering a $50,000 reward for information leading to the suspects’ arrests.

One of the armed robbers disarmed a female security guard, police and witnesses said. But a second security guard, Earl Coleman, 53, exchanged gunfire with the robbers, they said. At least 20 shots were fired.

Coleman and a bank customer, Dorothy Sanders, 73, a retired Chicago Public Schools teacher, were shot, authorities said. One robber may also have been wounded.

Coleman was shot in the chest and legs but was “doing good” at Advocate Christ Medical Center in Oak Lawn, said the mother of two of his children. Police said both individuals had nonlife-threatening injuries.