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Federal agents aggressively deployed powerful chemical irritants during Operation Metro Surge, a recent report found, in many cases at close range on protesters.

, conducted by the Physicians for Human Rights and the Human Rights Center at the University of California Berkeley, was released earlier this month. Researchers compiled and verified use-of-force incidents between June 2025 and June 2026 through documentation including news reports, legal filings and social media posts.

The study identified 412 incidents when law enforcement misused crowd control weapons during that period, of which 94 — or nearly a quarter — occurred in Minnesota. Almost all of the Minnesota cases took place in the Twin Cities during Operation Metro Surge, when thousands of federal officers descended on the state between December 2025 and February 2026. The study focuses on incidents researchers determined were unsafe, not those deemed just disproportionate or excessive. 

Injuries documented nationwide in the report that were caused by crowd control weapons include traumatic brain injuries, burns and serious fractures. Vulnerable people such as children, pregnant women and those with disabilities were targeted, along with protected people like journalists, the study says. 

“It’s a systemic issue,” Kimberly Saltz, a legal fellow at the Physicians of Human Rights, told Sahan Journal. “This is not a one-off. This is not a singular bad actor. This is showing a very clear pattern of misuse.”

, which pinpoints each use-of-force incident across the country. The report emphasizes the data is an undercount — researchers were only able to include incidents where they had enough information and evidence to do so.

In a statement, the U.S. Department of Homeland Security said federal officers are trained to use the minimum amount of force necessary “to resolve dangerous situations to prioritize the safety of the public and our officers.”

Compared to other cities, like Los Angeles, which saw a large amount of the use of kinetic impact projectiles like rubber bullets, the study found Minneapolis saw excessive use of chemical irritants like tear gas. 

“I think we were all shocked by the just sheer amount of chemical agents being used,” said Sasha Schell, the supervising reporter at the Human Rights Center who worked on the study.

Schell said the “weapon of choice” in Minnesota was a spray called MK-9, a powerful pepper spray in a fire-extinguisher-like canister. The spray has a reach of 15 to 20 feet with no automatic shut-off, and is intended to be deployed at a distance of at least 6 feet. But the report said officers mostly used it at a closer range. 

Dr. Asha Hassan is a professor at the University of Minnesota Medical School who has studied the use of tear gas by law enforcement. She said deploying the spray at a closer distance can concentrate the dose people receive.

“We know the more somebody is exposed to, the more these symptoms escalate and get worse,” she said. 

Mild symptoms of tear gas exposure include irritation of the eyes and lungs. But more severe symptoms such as blindness or death can occur, she said. Children, pregnant people and those with chronic respiratory conditions may be more sensitive to chemical irritants. 

Hassan said the long-term impacts of chemical irritants are not well researched. She said it’s also concerning that they are largely unregulated, and it can be difficult for members of the public to know what they have been exposed to. 

“There’s so many things that are regulated that we are consuming, right? The food that we eat, the medications that we take. And yet this is not regulated,” Hassan said. “The onus is on the government. If they are using these chemical irritants that people are inhaling and consuming, then they have to justify that this is safe.”

In Minnesota, most of the crowd control weapons researchers identified were deployed by federal officers working under the U.S. Department of Homeland Security. Los Angeles on the other hand saw a large amount of weapons used by local police departments. 

However, one incident stood out to researchers in Minnesota, in which 

St. Paul police officers used chemical irritants

 on people as they gathered outside a home in November on Rose Avenue where federal agents were making an arrest. 

“That was one of the few local law enforcement incidents we actually had in the Twin Cities, which was sort of a surprising one for us when we found it,” Schell said. 

In a statement, the St. Paul Police Department said the officers’ actions are still under investigation. Internal and external complaints will be sent to the city’s Police Civilian Internal Affairs Review Commission.

“Our department understands the community’s desire to see the results of this investigation, and we share that want. We are committed to this being a thorough and complete investigation and unfortunately, that takes time,” the statement read in part. 

Hassan studied the use of chemical irritants by police in Minnesota following the murder of George Floyd in 2020. She said at that time, the irritants were mostly deployed by local law enforcement.

During Operation Metro Surge, she observed, the volume of chemical irritants deployed left large areas engulfed in tear gas, exposing more bystanders or people passing through the area – not just those who were participating in protests. The irritants can also linger in the air for hours after they’ve been set off.

The federal government’s use of chemical irritants during immigration actions was also the subject of several lawsuits, including one by the American Civil Liberties Union of Minnesota. 

sought an order for the federal government to stop engaging in practices — including use of chemical irritants — that the group believes violated the public’s First and Fourth Amendment rights while observing or protesting. A temporary order was put in place for a few days, but was soon dissolved. The lawsuit, which was filed in December, is still ongoing.

Alicia Granse, a staff attorney at the ACLU of Minnesota, said the organization received reports of agents spraying tear gas into cars, people being sprayed with irritants directly in the face and indiscriminate use of rubber bullets and flashbangs. 

Granse said when the government uses crowd control weapons like these, it can have a “chilling” effect on everyone, and is done to intimidate the public from continuing to protest. But she said despite the fatal shootings of Renee Good and Alex Pretti by ICE agents, Minnesotans continued to speak out.

“In the face of that, the people continue to go out and record, observe, and protest, despite this attempt by the government to chill them from doing that.”

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Immigration enforcement in Minnesota

The state accounted for nearly one-quarter of all incidents nationwide documented by the Physicians for Human Rights and the Human Rights Center at the University of California Berkeley. While rubber bullets were most common in Los Angeles, researchers found federal officers primarily used chemical irritants in Minnesota.

Aaron Nesheim | Sahan Journal

A person close their eyes while another person reaches around to help.

Chris Juhn for Sahan Journal

Smoke fills the night sky on a city street.

Study finds 94 cases of crowd-control weapon misuse during Minnesota ICE protests

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