A mother of four was raped and choked to death 15 years ago in her southwest Atlanta apartment.

Now, although the apartment building is gone, police investigators believe they have evidence pointing to someone who may have been at the scene.

In June of 1996, Patricia Sheffield, then 39, was found dead in her apartment in the 800 block of Booker T. Washington Road.

Police ran into a dead end investigating the murder, and Sheffield’s children – the oldest 12 and the youngest an infant – were disbursed to different homes in Georgia.

“We’ve been waiting for this day for a long time,” Sheffield’s second-oldest son, Aldo Sheffield, now 24, said of the day the case was reopened.

Detective Vince Velasquez,  homicide investigator and member of the Atlanta Police Department's complex and cold case unit, said police are looking for 49-year-old Robert Cowans, identifying him as a “person of interest.”

“Evidence that was present at that time in 1996, we’ve taken and reworked and looked at different possibilities of how that evidence can help us today,” Velasquez said, looking across a field of kudzu where Patricia Sheffield’s apartment building once stood.

“This person could be connected to Ms. Sheffield. We’re not saying he’s responsible for her death, but he’s certainly somebody we would like to talk to.”

Cowans is described as a 5-foot-6-inch black man weighing about 190 pounds. Police consider him a transient who may be traveling between homeless shelters.

On June 17 that year, Patricia Sheffield’s father couldn’t contact her by phone and began coming by the apartment and leaving notes. After four days of trying to reach her through messages, he had the apartment manager open her  unit.

There, she was found dead.

“We’re asking the public, if they know who he is, to contact us,” Velasquez said. “At the end of the day, he might be somebody who’s able to help us out.”

Sheffield had three sons and an infant daughter when she was killed.

In interviews Thursday with reporters from  AJC and Channel 2 Action News, her sons said they are looking for answers.

“I didn’t get to know Mom,” said John Sheffield, the oldest and now 27. “The last talk I had with her before she died, she said ‘take care of your brothers and sister.’ But I was 12 … I didn’t know what to do.”

Mario Sheffield longs for the day when he can see his mother’s killer face to face.

“I really want to ask the question, ‘Why?’” he said.

Velasquez stressed how important it is to find Cowans – to vet him as a potential suspect, just as much as to rule him out as one.

“There were other people of interest as well who we were able to locate, and we were able to sit and talk with and eliminate [as persons of interest],” Velasquez said. “They actually became our allies.”

But he reiterated that police didn’t view Cowans as a threat.

“He’s not somebody who we feel is a danger to anyone at this point,” Velasquez said of Cowans. “He’s just someone we need to cross off of our list.”

Patricia Sheffield’s children want to see justice done.

Mario Sheffield was 5 years old when his mother died.

“It was painful every day,” he said of growing up motherless. “One day, I hope to see her again, Lord willing.”

Aldo Sheffield joined with investigators in asking for help finding this next piece of the puzzle in his mother’s murder.

“I just ask people to picture this happening to them,” he said.

Anyone with information on Cowan or on the 1996 murder of Patricia Sheffield should contact Atlanta Crime Stoppers at 404-577-8477.