CPD released images and video of a man, wearing all black, and asked for the public's help in identifying him Tuesday.
"It's extraordinarily clear video, and obviously doesn't prove the commission of a crime, but it sure will lead the police to a suspect," ABC7 Chicago chief legal analyst Gil Soffer told the I-Team.
The video is crisp, and anybody who knows the man would undoubtedly recognize him.
The man who was shot died days later, the Cook County Medical Examiner's Office said.
The shooting happened before 4:30 p.m. last Wednesday near Clark Street and Fullerton Avenue.
Police said the 34-year-old man approached multiple people on the sidewalk before he was shot.
Person of interest wanted in Lincoln Park homicide
He was taken to the hospital, where he died Monday. He was identified Tuesday as Alexander Nesteruk of Wheaton.
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Multiple witnesses told ABC7 that Nesteruk had been roaming the block for much of the day, and had been behaving erratically, harassing and threatening pedestrians and hitting passing vehicles.
Around 4 p.m., witnesses said that Nesteruk encountered a man who was armed.
The fire department said Nesteruk was shot twice.
Witnesses told ABC7 he was shot in the chest, and the other man who was armed walked away calmly from the scene.
Chicago police said no arrests have been made.
Soffer said the video is a clear example of one major tool now in the hands of law enforcement.
"It is another great example of what we all know to be true about the world we're living in. There are cameras of all kinds in all places: store video, cell phones, a dozen other places that we can imagine. And everything we do, and nearly everything we do, is captured," Soffer said.
One estimate has Chicago with nearly 50,000 cameras in use, more than 18 for every 1,000 people.
"I think the better way to look at it is this video could be one piece of a much larger puzzle, and if the evidence comes piling in, then it will be joined by maybe eyewitness testimony, maybe DNA evidence, maybe articles of clothing that match the description or the picture of what we're seeing," Soffer told the I-Team.
In addition to tens of thousands of public cameras, atop poles and government buildings, there are thousands of additional private security cameras installed to monitor businesses.
People also have doorbell cameras at their front doors.
The video in the Lincoln Park case appears to be a from a street-level private camera.
Police frequently go door-to-door after neighborhood crimes searching for whatever video might help crack a case.
Anyone with information is asked to call Area Three detectives at (312) 744-8261, or submit an anonymous tip at CPDTIP.com.
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