A lone gunman herded seven adults and an infant into the back room of a small bank today and opened fire, killing four and wounding three before he fled, authorities said.

The FBI said it was not immediately known how much money the gunman took from the First Bank of Chattanooga branch in this town of 800, about 100 miles southwest of Oklahoma City.

The bank's female manager and two female employes, one of them six months pregnant, and a male bank customer were killed, police said.

The gunman left in a car after reportedly ordering the group into the back room, forcing the victims to lie on the floor and then shooting them in the head and back, City Marshal Tommy Dale said.

The weapon was believed to be a blue steel automatic pistol, FBI spokesman Dan Vogel said, adding that he did not know how many shots were fired.

The first person on the scene, Pam Matthews of Geronimo, said she entered the bank and found the lobby empty.

"I heard a baby crying. I kept hollering 'Is anybody here, is anybody here.' All I kept hearing was a baby crying.

"I walked to the back of the bank and found them all in one room. No one was moving. I think they felt maybe the robber was still in the bank. Only the baby was crying, and I ran out to get help."

Reuben Robles, 20, father of the infant, and his wife, Bellon, 15, went to a drive-in restaurant next door for help, Dale said. They were wounded and reported in good condition, but their child, 1-year-old Juanita, was not shot.

Dale identified the dead as bank manager Kay Bruno, in her 40s; employes Joyce Mullinex, in her 20s and six months pregnant, and Jeri Bowles, about 18, and customer Eddie Zeller, in his late 20s. One of the wounded, identified as Marilyn Roach, 24, was reported in critical but stable condition, officials said.

Authorities set up roadblocks surrounding the town in search of a man in his late 20s. He reportedly had a mustache, shoulder-length hair, green eyes and a thin build.

Vogel said the robbery occurred at about 1:30 p.m.

The FBI sealed off the bank and the adjacent area and helicopters from the Army's nearby Fort Sill Military Reservation aided in the search.

Billie Coast, two blocks away from the bank when the robbery occurred, said, "We didn't know anything had happened until we heard the sirens, police cars and ambulances and all kinds of excitement."

The bank, located in a one-story building in downtown Geronimo, has been open about a year.