No one has to tell Greg Hubler that murder is on the rampage in Atlanta.

The 31-year-old policeman was helping take the city's 133rd homicide victim of the year to the hospital when No. 134 literally fell into his lap.

The string of sensational deaths in Atlanta's unsettling summer began with the June 28 shooting of Dr. Marc R. Tetalman, a Columbus, Ohio, nuclear physician who was gunned down during a robbery on a downtown street.

The death total climbed last Tuesday night in a poor neighborhood of the city when Benjamin Langford, 22, of Atlanta ran screaming for help during another robbery.

Hubler was nearby, escorting an ambulance with victim No. 133 to the hospital. Langford ran to Hubler's car, tried to climb in and was shot by the pursuing robber. Langford slumped dead over the policeman. His assailant was arrested.

In the next 24 hours, six more Atlantans were killed, raising the city's homicide total for the first seven months of the year to 140, only three short of the total for all of 1978. (Eighty-two people were murdered here in the first seven months of 1978.)

"Crime With Vengeance; 6 Die in 14 Hours," read a banner Atlanta Journal headline in a flashback to the city's 1973 title as the nation's murder capital.

To the chagrin of politicians and business leaders in this convention center, the Atlanta Constitution called the city "one of the most murderous...in the world," where visitors "are shot routinely on main streets."

Police Lt. Jack Perry, who retired last week as head of the homicide squad, said, "We're at the point now where we're getting calls so fast we can't handle them all."

Perry called himself, at 52, "a mentally and physically exhausted man."

"I'm not running out," he said. "I can take the pressure. But I can't do the job I'm supposed to do. My men are frustrated. They're overworked and underpaid and they're doing the work of 30 men."

There are 19 detectives on the homicide squad.

The veteran detective's retirement was only one spinoff of the rising homicide rate.

Earlier, unidentified money-raisers, believed to be police officers, asked area businessmen for contributions to erect a billboard over a busy expressway near Atlanta Stadium: "Warning...You are now in the city of Atlanta, where police are underequipped, undermanned, underpaid. Proceed at your own risk."

Plans to erect the $3,500 billboard were canceled Friday after complaints from Mayor Maynard Jackson and the Chamber of Commerce.

J. K. Ramey, a tire company owner, said Jackson had threatened him because he had contributed to the billboard fund. He said that several weeks ago Jackson walked into his store and told him: "I'm going to put your a-- out of business."

A spokesman for Jackson said the mayor only wanted Ramey to stop using the street in front of his store to change tires, and knew nothing of the billboard fund contribution.

"The mayor doesn't use that kind of language," Angelo Fuster said.

In another development, Police Maj. W. W. Clark was demoted to lieutenant when he refused Police Chief George Napper's order to use his intelligence unit to find out who was behind efforts to erect the sign.

Meanwhile, the city broods over the reasons for its spiraling murder rate.

Psychologists and social theorists look to a variety of reasons, including unusually humid weather, economic uncertainty, and a lack of restraint in American society.

Perry links the homicide increase to a parallel rise in robberies: "When you're having 200 to 300 armed robberies a month, somebody's going to be shot."

Some observers blame the problem on the traditional turmoil in the Atlanta Police Bureau, which has been reorganized repeatedly during this decade and still occasionally buckles from racial strain.

The Chamber of Commerce cited a study that indicated that less than half of the 1,100-member force regularly get out from behind a desk for patrol work.

The rising homicide rate is not Atlanta's alone.Other major cities have reported sizable increases this year.

Police in Washington, D.C., said 123 people had been murdered there through yesterday afternoon, compared with 103 for the like period in 1978. Officials blamed the rise in part on unemployment and on increased drug traffic.

Still, Atlantans brood about their summer of death. As Paul R. Coverdell, a state senator from Atlanta, put it, "You get the sense that there's a loss of control."