A federal judge has determined that officers involved in the federal immigration enforcement initiative in Minnesota are prohibited from detaining or using tear gas on peaceful protesters, especially when these individuals are merely observing and not interfering with authorities.

This decision emerged from a lawsuit filed by the American Civil Liberties Union representing Minnesota activists.

Additionally, Minnesota, along with its major cities, Minneapolis and St. Paul, has initiated legal action against the Trump administration, arguing that federal officers are infringing upon the constitutional rights of residents in the Twin Cities.

According to officials, the Minnesota National Guard was deployed to support local law enforcement under the directive of Governor Tim Walz.

Guard units were dispatched to the location of the shooting and a federal facility where confrontations between officers and demonstrators have been a regular occurrence.

Information about what led up to the shooting was limited, Police Chief Brian O’Hara said.

Department of Homeland Security spokesperson Tricia McLaughlin said in a statement that federal officers were conducting an operation and fired “defence shots” after a man with a handgun approached them and “violently resisted” when they tried to disarm him.

In bystander videos of the shooting that emerged soon after, Pretti is seen with a phone in his hand but none appears to show him with a visible weapon.

O’Hara said police believe he was a “lawful gun owner with a permit to carry”.

DHS Secretary Kristi Noem said during a news conference that Pretti had shown up to “impede a law enforcement operation”.

She questioned why he was armed but did not offer details about whether Pretti drew the weapon or brandished it at officers.

The officer who shot him is an eight-year Border Patrol veteran, federal officials said.

The president weighed in on social media by lashing out at Walz and the Minneapolis mayor.

He shared images of the gun that immigration officials said was recovered and said: “What is that all about? Where are the local Police? Why weren’t they allowed to protect ICE Officers?”

Trump, a Republican, said the Democratic governor and mayor are “are inciting insurrection, with their pompous, dangerous, and arrogant rhetoric”.

Representative Alexandria Ocasio-Cortez of New York was among several Democratic politicians demanding federal immigration authorities leave Minnesota.

She also urged Democrats to refuse to vote to fund US Immigration and Customs Enforcement.

“We have a responsibility to protect Americans from tyranny,” she said, on social media.

Senate Democratic Leader Chuck Schumer later said that Democrats will not vote for a spending package that includes money for DHS, which oversees ICE.

Schumer’s statement increases the possibility that the government could partially shut down on January 30 when funding runs out.

Pretti was shot a little more than a mile (1.6 kilometres) from where an ICE officer killed 37-year-old Renee Good on January 7, sparking widespread protests.

Pretti’s family released a statement Saturday evening saying they are “heartbroken but also very angry” and calling him a kindhearted soul who wanted to make a difference in the world through his work as a nurse.

“The sickening lies told about our son by the administration are reprehensible and disgusting. Alex is clearly not holding a gun when attacked by Trump’s murdering and cowardly ICE thugs.

He has his phone in his right hand and his empty left hand is raised above his head while trying to protect the woman ICE just pushed down all while being pepper sprayed,” the family statement said.

“Please get the truth out about our son. He was a good man.”

Video shows officers, man who was shot

In a bystander video obtained by The Associated Press, protesters are heard blowing whistles and shouting profanities at federal officers on Nicollet Avenue.

An officer shoves a person who is wearing a brown jacket, skirt and black tights and carrying a water bottle. That person reaches out for a man, and the two link up, embracing.

The man, wearing a brown jacket and black hat, seems to be holding his phone up toward the officer.

The same officer shoves the man in his chest and the two, still embracing, fall back.

The video shifts to a different part of the street and then comes back to the two individuals unlinking from each other. It shifts focus again and then shows three officers surrounding the man. Soon at least seven officers surround him.

One is on his back, and another who appears to have a canister in his hand strikes a blow to his chest.

Several officers try to bring the man’s arms behind his back as he appears to resist. As they pull his arms, his face is briefly visible. The officer with the canister strikes him near his head several times.

A shot rings out, but with officers surrounding the man, it’s not clear where it came from. Multiple officers back off. More shots are heard. Officers back away, and the man lies motionless on the street.

The police chief appealed for calm, both from the public and from federal law enforcement.

“Our demand today is for those federal agencies that are operating in our city to do so with the same discipline, humanity and integrity that effective law enforcement in this country demands,” the chief said.

“We urge everyone to remain peaceful.”

Gregory Bovino of US Border Patrol, who has commanded the administration’s big-city immigration campaign, said the officer who shot the man had extensive training as a range safety officer and in using less-lethal force.

“This is only the latest attack on law enforcement. Across the country, the men and women of DHS have been attacked, shot at,” he said.

Walz said he had no confidence in federal officials and the state would lead the investigation into the shooting.

But Drew Evans, superintendent of the Minnesota Bureau of Criminal Apprehension, said during a news conference that federal officers blocked his agency from the scene even after it obtained a signed judicial warrant.

Demonstrations broke out in several cities across the country including New York, Washington and Los Angeles.

In Minneapolis, protesters converged at the scene of the shooting in Minneapolis despite dangerously cold weather — by the afternoon the worst of an extreme cold wave was over, but the temperature was still minus 6 degrees Celsius.

An angry crowd gathered after the shooting and screamed profanities at federal officers, calling them “cowards” and telling them to go home.

One officer responded mockingly as he walked away, telling them: “Boo hoo.”

Agents elsewhere shoved a yelling protester into a car.

Protesters dragged garbage dumpsters from alleyways to block streets, and people chanted “ICE out now” and “Observing ICE is not a crime.”

As dark fell hundreds of people mourned quietly by a growing memorial at the site of the shooting. Some carried signs saying “Justice for Alex Pretti”. Others chanted Pretti’s and Good’s names.

A doughnut shop and a clothing store nearby stayed open, offering protesters a warm place as well as water, coffee and snacks.

Caleb Spike said he came from a nearby suburb to show his support and his frustration.

“It feels like every day something crazier happens,” he said.

“What’s happening in our community is wrong, it’s sickening, it’s disgusting.”