CHICAGO (CBS) — An 57-year-old off-duty transit officer shot and killed an unarmed man in the Hermosa neighborhood on the Northwest Side.

Police are now saying the off-duty officer knew the man he shot.

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CBS 2’s Vince Gerasole is at the scene with new details on the investigation.

“He didn’t have any weapons,” said sister, Angelica Nieves. “He wasn’t doing anything wrong he was moving in furniture.”

Angelica Nieves is flush with anger and anguish. She said her brother, 38-year-old Jose Nieves, was shot to death by an off-duty Chicago police officer.

The shooting happened in the 2500 block of North Lowell around 9:13 a.m., according to Chicago police and fire officials. His sister said Nieves was moving furniture with his girlfriend.

“I have a lot more questions than I do answers at this time,” said Chicago Police Superintendent Eddie Johnson.

From Chicago’s top cop on down, a palpable sense of frustration stems from a 57-year-old mass transportation officer firing the fatal shots on an apparently unarmed man.

“The person who was shot did not have a weapon that much we know,” said Anthony Guiglielmi, CPD spokesperson. “The officers weapon is the only weapon involved.”

The officer did not just fire one shot, he shot multiple times, said Nieves.

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Police confirmed that the officer involved in shooting knew Nieves and the two were not strangers.

“These two individuals knew each other from a confrontation a few weeks ago,” Johnson said.

CPD said the officer was visiting the neighborhood and somehow got into a verbal argument with the victim, that escalated into several shots being fired on the street. WBBM’s Steve Miller reports.

Nieves was taken to Illinois Masonic Medical Center in critical condition, police said. He was later pronounced dead.

The family is now searching for answers.

“If you are an officer and you are getting shot at and your life is in danger I understand,” Nieves said. “But if a person doesn’t have a weapon, it doesn’t give you the right to take out your weapon and shoot at that person. It does not.”

A good portion of the neighborhood was cordoned off on Monday for the investigation, which left residents on edge.

“Over the past couple years, it’s been pretty good, no issues,” said Reuben Zarheoza. “We have a lot of kids coming, playing around here, so it’s kind of messed up to hear this happened a block away.”

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Both the Chicago Police Department and Independent Police Review Authority (IPRA) are conducting separate, but parallel investigations.