Stone Mountain -- A Stone Mountain Park attendant was on the phone with park police when she was shot and killed, authorities said Sunday.

At about 12:30 a.m. Saturday, a visitor asked Anita Redmon if he could re-enter the park through the west gate to retrieve a shoe, and she called police to notify them of the request, park police chief Chuck Kelley told WSB-TV.

The robber or robbers must have approached her at that moment, Kelley said.

"That's when the gate attendant said 'Signal 44, Signal 44, Signal 44', which is the code for armed robbery, "Kelley said. "And then our communications officers heard a pop."

Redmon, 63, was found dead in the gatehouse.

Investigators have found a witness who saw someone running near the scene, GBI Director Vernon Keenan said Sunday.

"A witness has given us information about seeing a figure running down the road," Keenan told WSB-TV.

Agents went door-to-door at a nearby apartment complex asking residents if they saw anything suspicious that night.

They also searched likely escape paths the killer may have taken.

"We're going to be looking for the weapon that was used in the murder and any other evidence that was discarded," Keenan said.

Authorities planned to bring a prisoner detail to the scene Monday to help with the search.

Stone Mountain Park said this was the first such incident in the park's history. It offered a $20,000 reward for help in finding the killer.

The park hired Redmon in April. She was 25-year veteran of the Doraville Police Department, retiring in 1999 with the rank of sergeant.

"The priority at Stone Mountain Park is the safety of the people that come here, whether they work here or visit here," said Chief Chuck Kelly of the Stone Mountain Park police. "She was an outstanding lady, an outstanding police officer. It's just a tragic loss for somebody that devoted her entire life to public safety and then in their retirement -- some senseless crime like this -- they're shot doing a job that they love."

Channel Two correspondent Tom Jones contributed to this report.