Who's killing homeless men in Atlanta?

• Detective: "I don't know why someone would shoot two defenseless men"


• Shootings happened within 3 miles of each other


• The bullets used are fairly distinctive

Atlanta (CNN) -- Atlanta police are calling the shootings "sinister" because whoever pulled the trigger wasn't expecting to gain from them monetarily.

These were two homeless men, shot to death as they slept. And police aren't convinced the threat is over.

"A lot of our shootings involve robbery. A lot of our shootings involve someone making good on an old debt or some kind of revenge factor," Atlanta police Detective David Quinn told reporters Wednesday.

"I don't know why someone would shoot two defenseless men."

The shootings happened over the Thanksgiving week within three days of each other. The killer, or killers, haven't struck since, but police are asking the city's homeless to remain vigilant.

"We have the Christmas holidays coming up. We're asking for anyone's help," Quinn said.

Three days, three miles apart

The first shooting took place November 23.

Dorian Jenkins was fatally shot five times as he slept, wrapped in a blanket, on a sidewalk in downtown Atlanta.

Less than three days later, Tommy Mims didn't show up as normal at a recycling center where he took cans and other scrap metals to sell.

Mims, known locally as "Can Man" was found dead under a bridge where he usually slept. His body, also wrapped in a blanket, was riddled with seven bullets. He was killed less than three miles from Jenkins.

"They never came out of the sleep they were already in," Quinn said. "They weren't fleeing, running. They were asleep when they took these rounds."

Tellings details

Here's why police think the killings are related.

The rounds used in both shootings are fairly distinctive: .45-caliber bullets that, according to Quinn, haven't been made since 2010.

They were fired from revolvers, either a Taurus "Judge" or a Smith & Wesson "Governor." That reveals another troubling fact.

"These guns have a capacity of five or six rounds," Quinn said. But Mims, the second victim, had been shot seven times.

"Someone had to reload the gun in order to get seven rounds in him."

No suspect, motive

Police have no suspect nor a motive. Two witnesses offered detectives similar descriptions: someone dressed in dark clothing.

Police are asking "homeless brothers and sisters to look out for one another."

They're urging them to "use the buddy system" and bed down together with "someone that can actually watch their backs."

Quinn said on Thanksgiving evening, he went to Mims' family home to break the news of his death.

"His family never sees him until Thanksgiving Day," he said. "They were waiting on him to show up."