MINNEAPOLIS—A U.S. Border Patrol officer shot and killed a 37-year-old man here Saturday morning, authorities said, dramatically escalating an already tense standoff between Minnesota and the federal government in the wake of an earlier fatal shooting by a federal agent.

The new incident exploded on Saturday morning, when Alex Pretti, an intensive-care nurse , was wrestled to the ground by several agents and then fatally shot by a Border Patrol officer after he was confronted while filming the activities of U.S. Immigration and Customs Enforcement officers.

The city has been a tinderbox since the fatal shooting of Renee Good, also 37 and a Minneapolis resident , by an ICE agent. After that incident, the agent who fired the shots, Jonathan Ross, was whisked away from the scene, and Good was instantly labeled a “domestic terrorist” by Trump administration officials. Local law-enforcement officials were blocked from conducting an investigation.

Immediately after Saturday’s shooting, Minnesota Gov. Tim Walz and other local officials attempted to draw the line against the federal law-enforcement operation that has turned the Twin Cities into a battleground. Minneapolis Police Chief Brian O’Hara said he ordered his officers to stay at the scene after they were told they weren’t needed. O’Hara described Pretti as a legal gun owner with no criminal record and said he wasn’t aware of past interaction with law enforcement beyond traffic tickets.

“Minnesota’s justice system will have the last word,” Walz said.

Trump administration officials had different ideas. They labeled Pretti a “domestic terrorist,” echoing the Good case, and gave no indication that they would launch a civil-rights investigation examining whether the agent who fired on Pretti used excessive force—normally a common step after such shootings.

Shock and anger rippled through Minneapolis, where a day earlier thousands of Minnesotans marched in subzero temperatures against the immigration enforcement surge. “He’s a typical Minneapolis guy,” said Gretchen Unger, who previously worked with Pretti at a biology startup. “He’s the furthest thing from a domestic terrorist, or whatever stupid thing they’ll come up with.”

Dozens of demonstrators gathered near the site of the shooting in a face-off with officers. A few officers were masked and some wore Border Patrol logos. Witnesses reported that officers were using pepper spray, pepper balls and a flashbang on protesters nearby.

man shot Minneapolis

One protester hit and cracked the windshield of an unmarked white van belonging to officers. People shouted “Shame on you” from their balconies to officers below.

Videos of the incident appear to show that before the shooting, Pretti was filming federal agents, something that has become common in Minneapolis as citizen observers document ICE actions . Agents appeared to spray a chemical irritant at him and another person. In the milliseconds before shots were fired, it was less clear what happened during a scuffle in which Pretti was on the ground, surrounded by multiple agents.

Amid rounds of gunfire and screams, people who had been observing and filming the federal agents continued to blow whistles and yell at them.

man shot Minneapolis

The Department of Homeland Security said the man was shot after he approached officers with a handgun. “The officers attempted to disarm the suspect but the armed suspect violently resisted,” DHS said. Video shows several masked agents struggling to push a man to the ground before gunfire is heard.

He was pronounced dead on the scene, DHS said. The officer who shot him was an eight-year veteran of Border Patrol, according to federal officials.

The Trump administration has flooded Minneapolis and greater Minnesota with more than 3,000 agents in a weekslong campaign DHS has described as the largest operation in its history and one meant to root out illegal immigration following a sweeping welfare-fraud scandal that put the state’s Somali community in the national spotlight.

Minnesota officials have described the stated reasons as a pretext for President Trump to punish a state that didn’t vote for him and a Democratic governor he sees as a nemesis.

“As I said last week, this federal occupation of Minnesota long ago stopped being a matter of immigration enforcement,” Walz said at a news conference. “It’s a campaign of organized brutality against the people of our state. And today that campaign claimed another life.”

Saturday’s shooting was the third this month in Minneapolis. A week after Good was shot on Jan. 7, a federal officer shot and injured a Venezuelan man after he tried to flee a traffic stop, DHS said.

On Friday, an FBI supervisor in the Minneapolis field office resigned after leadership in Washington pressured her to end a civil rights investigation into the agent who shot and killed Good, people familiar with the matter said. The probe of her killing has instead focused on Good and her partner, and any ties they may have had to protest groups in Minneapolis, people familiar with it said. Complicating matters in the Good case: Federal officials have refused to cooperate with state and local authorities in their efforts to investigate the shooting.

man shot Minneapolis

A Justice Department spokesman didn’t immediately respond to requests for comment Saturday, but Attorney General Pam Bondi made no mention of the agent’s conduct and blamed the state’s Democratic leadership for any violence in Minneapolis.

“Federal law enforcement agents are doing heroic work to remove the worst of the worst in Minnesota—and they’re only there in the first place because of Walz, Ellison and Frey’s dangerous sanctuary policies,” she said in a post on X calling out the governor, Minnesota Attorney General Keith Ellison and Minneapolis Mayor Jacob Frey. “Now Minnesota’s ‘leaders’ are creating the conditions for violence against law enforcement.”

Walz said he was in contact with the White House and called for an end to the immigration crackdown in the state.

“The President must end this operation. Pull the thousands of violent, untrained officers out of Minnesota. Now,” Walz said on social media. The Hennepin County Sheriff’s Office said Saturday it had requested assistance from the Minnesota National Guard.

Maj. Gen. Shawn Manke, adjutant general of the Minnesota National Guard, told reporters that some of his soldiers have been activated for more than a week and they are helping local law-enforcement agencies which have been stretched thin during the federal activity in the state. He declined to state the exact number of those deployed but said the total is “adequate for the requests we have right now” and that the National Guard is “bringing more resources that will be able to respond in a timely manner.”

Walz said the state would be “billing the federal government for the cost of the National Guard because they are incurring the costs that are falling on us by their reckless actions.”

Trump accused Walz and Frey of inciting an insurrection, saying that ICE agents were arresting criminals and removing them from the state. “LET OUR ICE PATRIOTS DO THEIR JOB!,” Trump said on social media .

Write to Joseph Pisani at joseph.pisani@wsj.com , Mariah Timms at mariah.timms@wsj.com , Sadie Gurman at sadie.gurman@wsj.com and Neil Mehta at neil.mehta@wsj.com

Corrections & Amplifications undefined Minneapolis is in the southeastern half of Minnesota. An earlier version of the map in this article incorrectly showed the city in the northwest of the state on some screen sizes. (Corrected on Jan. 24)