Organizers of the protests said that they were canceling all of the planned events in Minnesota after a recommendation to do so from Gov. Tim Walz and other officials.

Several thousand people had gathered outside of the State Capitol in St. Paul by early Saturday afternoon, about 25 miles from the shootings.

Governor Walz said that people should “not attend any political rallies” in the state until the suspect was taken into custody.

The police said that the suspect had a list of targets and that both of the state lawmakers who were shot were on the list.

The gunman impersonated a police officer, the authorities said, and killed State Representative Melissa Hortman and her husband, Mark, at their home before going to the home of State Senator John A. Hoffman and shooting him and his wife, Yvette. The Hoffmans are being treated at a hospital.

Bernard Mokam and Ernesto Londoño contributed reporting.

State Senator John A. Hoffman and his wife, Yvette, were also shot multiple times in an earlier attack by the same assailant. Mr. Hoffman and his wife remained alive on Saturday morning. A search is underway for the gunman, who officials said was impersonating a police officer when he carried out his attacks.

Both state lawmakers who were shot served critical roles in the Minnesota Legislature as members of the Democratic-Farmer-Labor Party, which functions as the state’s Democratic Party. Ms. Hortman served as speaker of the Minnesota House of Representatives for a six-year period that ended this year, and she led her party’s push to retain power during the chaotic start to the session. Mr. Hoffman, a fourth-term state senator, chairs the Senate Human Services Committee.

Before the shooting, Democrats and Republicans each held 67 seats in the lower chamber. Gov. Tim Walz could call a special election to fill Ms. Hortman’s position. Democrats hold a one-seat majority in the Senate.

After last November’s election, Democrats and Republicans were tied for control of the lower chamber. But when a judge determined that one of the newly elected Democrats had not met the residency requirements to run for his seat, Republicans won a narrow majority and sought to capitalize on it.

Minnesota Republicans used their temporary narrow majority to push several contentious bills, including one that would bar transgender girls from competing in girls’ sports and another that would limit the governor’s emergency powers. Those bills failed to pass but inflamed partisan tensions.

That majority was short-lived because a Democrat won a special election for the newly vacant seat in March. Ms. Hortman had said in January that her members intended to stay away from the capital, holding off any business until Democrats regained the seat.

House Democrats refused to show up in the State Capitol on opening day, but Republicans unilaterally continued business, choosing Representative Lisa Demuth as their House leader. House Democrats called the move outrageous and filed a lawsuit, asking the Minnesota Supreme Court to bar Republicans from conducting business.

The chaotic start to the session underscored the challenges that Mr. Walz, a Democrat, faced on his return to Minnesota after he spent part of last year campaigning to be vice president.

Without full control of the Legislature — which they had held the previous two years — Democrats faced significant challenges in passing their priorities. The Minnesota Senate was also closely divided.

Lawmakers failed to pass a balanced budget when the session ended in May, leading Mr. Walz to call a special session.

Lawmakers passed a $66 billion budget after a daylong special session, averting a partial government shutdown that would have begun in July.

In July 2024, a gunman shot at Donald J. Trump at a campaign rally in Butler, Pa., grazing his right ear and killing a spectator. Two others were critically injured. Just over two months later, Secret Service agents traded fire with a man they called a second would-be assassin at one of Mr. Trump’s golf courses in Florida.

In April, a man was charged with setting fire to the residence of Gov. Josh Shapiro, Democrat of Pennsylvania. Not long before, the Republican Party headquarters in New Mexico and a Tesla dealership near Albuquerque were firebombed, at the height of Elon Musk’s involvement in the Trump administration. Those attacks came as rancor toward Mr. Musk’s slashing of the federal government prompted a wave of arson and vandalism against Tesla dealerships.

And less than a month ago, a man gunned down a pair of workers from the Israeli Embassy in Washington.

The attacks occur against the backdrop of mounting threats against judges and lawmakers, and as political violence — and the threat of it — has become increasingly common in America. In recent years, attacks have targeted former Speaker of the House Nancy Pelosi and her husband, a mayoral candidate in Louisville, Ky., and Republican congressmen practicing for the annual Congressional Baseball Game.

She played a key role in passing a trove of bills during the 2023 session, when Democrats held a slim majority in the Legislature, including legislation that expanded abortion rights, legalized recreational marijuana and required employers to offer paid family and medical leave.

This year, under Ms. Hortman’s leadership, Democrats in the House boycotted the early weeks of the legislative session amid a fight for control of the chamber. Voters last year left Democrats and Republicans with an equal number of seats in the House, but challenges to two of the elections won by Democrats created a period of uncertainty around which party would control the chamber.

When those challenges were settled, Ms. Hortman agreed to let the top Republican in the House, Representative Lisa Demuth, serve as speaker.

Colleagues have long praised Ms. Hortman’s work ethic, negotiation skills and pragmatism.

Jerry Gale, Ms. Hortman’s campaign manager, said in an interview that she was a tireless campaigner who was passionate about recruiting fellow Democrats to run for office.

“She had a vision of what she wanted the state to be like, and she knew it was going to take a lot of work,” Mr. Gale said.

As the political rhetoric in the state grew more acrimonious in recent years, Mr. Gale said, Ms. Hortman worried about her safety.

“I think it did cross her mind at times on the campaign trail,” he said. Her own style was not combative, however. On the campaign trail and in the Capitol, Ms. Hortman kept her remarks short, to the point and civil, he said.

Ms. Hortman was married with two children, according to her state legislative biography. Her husband, Mark, was also shot and killed on Saturday.

Sen. John A. Hoffman has served in the Legislature since 2013. Before being elected, he served as a member of the Anoka-Hennepin School Board for several years.

Gov. Tim Walz of Minnesota said the Hoffmans had both undergone surgery. “We are cautiously optimistic that they will survive this assassination attempt,” he said.

Mr. Hoffman, 60, was born in Casper, Wyo., and formerly made a living as a marketing and public relations professional. He and his wife, Yvette, have a daughter. They live in Champlin, a suburb north of Minneapolis. His home address was published on his biographical page on the Senate’s website.

Mr. Hoffman chairs the Senate’s Human Services Committee. He is a fourth-term senator, and won his most recent election by 10 percentage points.

“A hallmark of my approach is collaboration across the aisle,” Mr. Hoffman wrote in a letter to constituents ahead of last year’s legislative session. “I firmly believe that the path to progress for our state involves considering input from all perspectives, regardless of which party holds the majority.”

On his campaign website, Mr. Hoffman said he was particularly proud of his efforts to make it easier for people with disabilities to work. He also described himself as a conscientious steward of taxpayer dollars.