A recent Channel 3 News investigation combed through more than a decade of Cuyahoga County Medical Examiner’s records to determine which homicides fit the pattern of a serial killer.

Cases involving victims who were stabbed, strangled, or killed by blunt force were set aside.

Through a collaboration with the Plain Dealer, the unsolved cases were then separated from there.

In all, 61 murders since 2004 were determined to fit a serial killer pattern, and that information was then shared with Tom Hargrove, a self-described “homicide archivist.”

Hargrove launched the not-for-profit “Murder Accountability Project” which has compiled the most complete database of murders in the country, as well as a computer formula that can find patterns in those killings.

In Cleveland, he noticed “a pattern of older women being killed by non-firearms methods, a more intimate kind of killing,” he said, as well as “two clusters” of murders on the city’s east side,

The first cluster was along the eastern portion Euclid Avenue.

WKYC

The second was along East 93rd Street.

WKYC

He concluded that whoever was responsible likely had access to a car and “was organized.”

He also concluded that Cleveland could have as many as three active serial killers, warning that if the killers are not brought to justice, the killing could continue.

“It really is common sense,” he said. “If you leave a killer walking the streets, oddly, the killing goes on.”

Hargrove says he has worked with the Cleveland Police Department and believes they are doing a good job, however, suspects they may not be assigning enough detectives to homicides.

He said it is not just a problem in Cleveland, but across the nation, where homicide arrest rates are down.

According to the FBI, only 59% of homicides resulted in arrests in 2016.

“That’s the lowest clearance rate ever recorded in the United States,” he said. “It is the lowest we ever heard of in any western nation. It is a national tragedy.”

It is also a local one for at least 61 victims’ families who still believe that murderers are on the loose.

WATCH: WKYC's Andrew Horansky and The Plain Dealer's Rachel Dissell discuss their joint investigation on Facebook Live