Investigators are trying to determine if a suspect who shot two men, execution-style, four years ago in Chicago could be the same suspect responsible for six murders in the last year and a half in Stockton and Oakland.

The "Duck Walk Killer" caused terror in the Chicagoland area in early October 2018, after the shooting deaths of two men out walking in Rogers Park — a community about nine miles north of downtown Chicago, along Lake Michigan, that is home to Loyola University. As KPIX reports, the first victim was 73-year-old Douglass Watts, who was shot on the street while out walking his two dogs on September 30, 2018. The second victim, 24-year-old Eliyahu Moscowitz, was killed while walking along a bike path near the university, about 36 hours later.

The two killings were linked by ballistics evidence.

Chicago residents were shocked by the killings, which were followed by the release of surveillance video of a suspect wearing a ski mask over his head and face — a bit less common and more sinister in the pre-pandemic times. He appeared in daylight video to be a Black male around six fee tall, with a distinctive gait and slightly outward-turned feet — leading to the "duck walk" moniker.

Rumors spread around the Loyola campus and the neighborhood in the months following the unsolved shootings, and residents continued discussing where the killer might have gone. During the pandemic, a Facebook Group devoted to the shootings surmised that the killer might be quarantining while caring for an elderly parent, or he might be incarcerated for another crime, or he might have left the Chicagoland area.

CBS Sacramento broke the story of the possible connection between this killer and the man who has been terrorizing the homeless community, and the larger community, in Stockton for the last several months. The Stockton serial killer, as we've been calling him, killed five homeless men in the city between July and September of this year, the most recent just a few weeks ago. Police quickly determined that the same gun was used to kill a homeless man in Oakland in April 2019.

A Sacramento reporter got in contact with CBS Chicago Investigator Brad Edwards, who immediately saw similarities in the brief, much more obscured surveillance video that is some of the only evidence in the Stockton case.

"Over and over and over we heard 'pay attention to the gait, the gait...the walk' and it struck a chord," Edwards said, speaking to CBS Sacramento. Looking at the figures in both videos, Edwards says, "They're eerily similar in stature, clothing, and that gait. It was very close as far as what appeared to be the same height, 6 to 6'2", weight, the same slender clothing, hands in pockets."

As Edwards says, the Duck Walk Killer shootings stood out for their randomness — neither man was robbed, both were point-blank-range shootings on the street — even in a city where nearly 3,000 people were shot in 2018, and 561 murders took place that year.

"This double murder that happened struck a chord in Chicago — no one's forgotten about it, and we have a lot of crime in Chicago," said Edwards, speaking over Zoom with CBS Sacramento on Thursday.

As of Friday morning, both Chicago police and Stockton police say they are working together, but they have not found any connection between the killings so far — and that may imply that the ballistics on the guns used don't match up, so all they have to go on is this "gait" stuff. The nature of the killings do appear different — all the Stockton shootings and the Oakland one, including one non-fatal shooting of a homeless woman, took place in late-night hours when few people were on the street, in areas with little surveillance. The Chicago shootings took place in daylight, and the victims were both walking on the street, while in the Oakland and Stockton shootings the victims were all unhoused, and at least we know the surviving female victim was inside her tent.

"As part of our investigation, we have reached out to numerous law enforcement agencies in our state and across the nation," Stockton Police Public Information Officer Joe Silva said Friday. "We did our due diligence reaching out to Chicago PD based off the videos we have seen of their suspect.  At this time though, we do not have anything linking the two investigations. At this time, it appears the two are not related."

The most recent killing took place on September 27, when a 54-year-old man was killed in Stockton.

On Thursday, Stockton police held several informational sessions with members of the local homeless community and service providers, and they say that they, "answered questions, addressed concerns, and distributed flyers containing personal safety tips."

Previously: Residents of Stockton — Especially the Homeless — Are on Edge Over Possible Serial Killer on the Loose