The Minnesota Star Tribune identified the victim as Alex Jeffrey Pretti, a 37-year-old Minneapolis resident and US citizen.
Investigative journalist Jacqueline Sweet reported that Pretti was a registered nurse with ties to Colorado and Wisconsin, describing him as an athlete, a son, and a brother.
A physician who worked with Pretti at the US Department of Veterans Affairs said he served as an ICU nurse.
Various social media and eyewitness reports showed ICE agents shot and killed Pretti during another deadly operation to round up undocumented immigrants in Minneapolis in the third week of a crackdown that garnered fatalities and widespread condemnation.
Alex Pretti
Sweet also cited an eyewitness who told The Intercept that Pretti was among several legal observers who mobilized earlier that morning outside a doughnut shop where federal agents were operating.
The witness said Pretti and others hid in a doorway, fearing they would be shot as well.
An ICE agent confronts Pretti as he attempts to film their conduct shortly before he was killed. Social media
A video circulating on social media shows ICE agents tackling two individuals, a man and a woman, monitoring the protests and officers' conduct on the ground. The officers deployed what seemed like a chemical agent at the individuals before firing shots , killing a man.
The killing of Pretti came less than three weeks after US citizen Renee Good was shot and killed by an ICE officer involved in sweeps to round up undocumented migrants.
The Department of Homeland Security insisted its officers acted in self-defence while seeking "an illegal alien wanted for violent assault" in a "targeted operation."
But Minnesota Governor Tim Walz called the shooting "horrific" and demanded that state authorities lead the investigation.
A video circulating on social media -- and later confirmed by authorities -- shows several agents, including at least one wearing a vest marked "POLICE," surrounding a person on the ground and hitting him multiple times. Several gunshots are heard.
Minneapolis Mayor Jacob Frey pulled no punches, urging President Donald Trump to end the federal immigration operation, which has sparked sometimes violent demonstrations.
"This is a moment to act like a leader. Put Minneapolis, put America first in this moment -- let's achieve peace. Let's end this operation."
Federal immigration officers deploy tear gas at protesters after a shooting in Minneapolis. AP
Police chief Brian O'Hara said an "incredibly volatile scene" had erupted after the shooting and urged residents to avoid the area.
Officers who declared the protest an unlawful assembly deployed clouds of tear gas as the crowd grew and used dumpsters to make blockades on the road in the busy south Minneapolis neighborhood known for its restaurants.
The Department of Homeland Security claimed on X that "an individual approached US Border Patrol officers with a 9 mm semi-automatic handgun" and that its officers tried to disarm the man who they say "violently resisted."
"Fearing for his life and the lives and safety of fellow officers, an agent fired defensive shots. Medics on scene immediately delivered medical aid to the subject but was pronounced dead at the scene," DHS said.
O'Hara said police believed the victim was a "lawful gun owner with a permit to carry."
Minnesota allows the open carrying of firearms with a permit.
'Horrific shooting'
Earlier, Walz said he had discussed "another horrific shooting by federal agents" with the White House.
"Minnesota has had it. This is sickening," he said on X.
"The President must end this operation. Pull the thousands of violent, untrained officers out of Minnesota. Now."
Thousands of ICE agents have been deployed to the Democratic-led city, as Trump presses a sweeping campaign to deport undocumented migrants.
Minneapolis has been rocked by increasingly tense protests since federal agents shot and killed Good, a US citizen, on January 7.
An autopsy concluded that the killing was a homicide, a classification that does not automatically mean a crime was committed.
The officer who fired the shots that killed Good, Jonathan Ross, has neither been suspended nor charged.
The detention of a five-year-old boy this week, as agents sought to arrest his father, rekindled public outrage.
"Donald Trump and all your lieutenants who ordered this ICE surge: watch the horrific video of the killing today. The world is watching," Democratic Senator Amy Klobuchar said on X.
*This story was compiled by Ahram Online.
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