On a late summer’s evening in 1985, she phoned the National Rifle Association headquarters and left a blunt message: “My name is Sarah Brady, and you’ve never heard of me, but I am going to make it my life’s ambition to try to put you all out of business.”

With that call, Mrs. Brady started down a road that would make her the public face of gun-control activism for a generation. Her husband, James S. Brady, was Ronald Reagan’s press secretary and was left paralyzed during an assassination attempt on the president in 1981. She was left to care for her husband through his long, at times excruciating, convalescence. He died Aug. 4, 2014, at age 73.

But it wasn’t her husband’s shooting that led Mrs. Brady to call the NRA. The turning point for her activism came four years later, when their 6-year-old son, Scott, found what he thought was a toy gun and pointed it at his mother. She told him never to point a gun at anyone and, when he handed it to her, she found to her horror that it wasn’t a toy but a fully loaded .22 similar to the one used to shoot her husband.

“The maddest I’ve ever been in my life,” she told The Washington Post of the gun incident with her son that occurred during a visit to her husband’s home town in Centralia, Ill. “I was livid.”

Mrs. Brady grew into a determined foe of the NRA, one of most powerful lobbying organizations in the country. She died April 3 at a retirement community in Alexandria, Va. She had pneumonia, a family spokeswoman, Gail Hoffman, said.

Jim and Sarah Brady make their way to the podium at the 1996 Democratic National Convention. (Keith Jenkins/The Washington Post)

A lifelong Republican, Mrs. Brady reached out to a small organization, Handgun Control Inc., now the Brady Campaign to Prevent Gun Violence, and joined its efforts by writing letters to members of Congress as well as lobbying them in person on Capitol Hill. She was the driving force behind the gun-control legislation known as the Brady Bill, signed into law by President Bill Clinton in 1993, and her pointed language and GOP background lent greater credibility to the cause.

To gain support for the Brady Bill, which required a waiting period and background check on all handgun purchases through federally licensed dealers, Mrs. Brady lobbied politicians, appeared on TV talk shows, wrote op-ed pieces and made speeches often to audiences packed with hostile NRA supporters.

During a 1992 appearance by Mrs. Brady and her husband at the University of Nevada at Las Vegas, for instance, the audience in the packed gymnasium was filled with NRA supporters, many bused in from California. The heckling started early and, at nearly every point, Mrs. Brady’s remarks were refuted with shouts of “liar, liar.”

In her 2002 memoir, “A Good Fight,” written with Merrill McLoughlin, Mrs. Brady noted that at the end of her speech, the curtain came down and she and her husband were escorted off the stage by police officers — some armed with semiautomatic weapons.

The NRA tried to discredit her by claiming that the gun-control lobby was using her to create an emotional campaign.

“I think it’s hysterical,” she told The Post in 1986, “that they talk about me being emotional and their members around the country use scare tactics saying, ‘The liberals are taking our guns away. Do something!’ ”

With the continued strength of the NRA and the failure to advance gun-control legislation in the past 20 years, it is somewhat difficult to assess Mrs. Brady’s lasting impact. But it is clear that her efforts helped galvanize support for the Brady Bill, the first gun-control measure passed in a generation.

She was also effective in bringing new support into the battle for handgun control, including from several leading law enforcement organizations throughout the country. To that degree, she was a serious threat to the NRA and its rigid hands-off policy on gun legislation.

After joining Handgun Control, Mrs. Brady’s first order of business was trying to stop the NRA-backed McClure-Volkmer bill in Congress. It aimed to repeal key provisions of the 1968 federal gun-control act, which set age limits on gun purchases and banned the importation of handguns known as Saturday night specials.

While the Senate ultimately enacted McClure-Volkmer — sometimes called the Firearm Owners Protection Act of 1986 — lobbying by Mrs. Brady, other gun-control advocates and some law enforcement groups led to the adoption by the U.S. House of a watered-down version that did little to weaken the 1968 law.

In a 1990 New York Times profile of Mrs. Brady, the NRA chief lobbyist James Jay Baker conceded that she “had been very effective.” He qualified his comments, noting that her influence in the gun-control debate was also “based on emotion.”

Taking the message nationwide

The Brady Bill was first proposed in 1987. Its key provisions were a background check and a seven-day waiting period before a gun purchase transaction could be completed. The NRA’s opposition was swift and firm.

The bill had a tortured time in Congress, with NRA-allied lawmakers from both sides of the aisle imposing roadblocks to its discussion, much less an up-or-down vote.

During the years the Brady Bill was stalled in Congress, Mrs. Brady took her gun-control message around the country. Her high profile lent strong support in several states — including California, New Jersey and Virginia — that adopted gun-control statutes. The measures often contained provisions mandating a waiting period and background checks for the purchase of assault weapons and handguns.

Mrs. Brady became a political independent as her involvement in the gun-control campaign evolved. She backed Democrats such as former U.S. senator and 2004 presidential candidate John F. Kerry of Massachusetts, now the secretary of state, who supported gun control. In 1992, she supported Democratic presidential candidate Bill Clinton after President George H.W. Bush, a lifetime NRA member, refused to commit to supporting the Brady Bill.

The NRA’s legal efforts to overturn the Brady Bill led to a 1997 U.S. Supreme Court ruling that declared that under the 10th Amendment, state and local law enforcement officials could not be forced to handle the background checks required by the law.

The overall Brady statute, however, was upheld. A year later, the FBI’s National Instant Criminal Background Check System came online and sped the process of checking prospective gun buyers.

Sarah Jane Kemp was born Feb. 6, 1942, in Kirksville, Mo. Her father worked for the FBI and moved the family to Alexandria, where she graduated in 1959 from Francis C. Hammond High School.

After earning a bachelor’s degree in 1964 from the College of William and Mary in Williamsburg, she got a job teaching fourth grade in Virginia Beach. By the summer of 1968, she had become more politically active — she opposed the war in Vietnam — and decided not to renew her teaching contract.

She soon became an assistant to the campaign director at the National Republican Congressional Committee in Washington and met James Brady, who was seeking funds for a candidate he was managing in Illinois. They were married in 1973.

Survivors include a son, James “Scott” Brady Jr. of Rehoboth Beach, Del.; a stepdaughter, Melissa “Missy” Brady Camins of Woody Creek, Colo.; and a brother, William Kemp of Arlington, Va.

Through the 1970s, Mrs. Brady worked for two GOP congressmen before returning to the Republican National Committee as its director of administration and coordinator of field services. She left the committee to be a stay-at-home mother after her husband joined Reagan’s successful presidential campaign in 1980.

The shooting

On March 30, 1981, James Brady left a gathering with the AFL-CIO at the Hilton Hotel in Washington while accompanying Reagan. A young man named John W. Hinckley Jr. began firing, and the first bullet struck Brady above the left eye.

In addition to the president, Secret Service agent Timothy McCarthy and D.C. police officer Thomas Delahanty were also injured in the attack. Brady, Reagan and McCarthy were taken to George Washington University Hospital. Delahanty was taken to the Washington Hospital Center, now known as MedStar Washington Hospital Center. All survived.

Three TV networks erroneously reported James Brady’s death after the shooting. Mrs. Brady, home at the time of the incident, rushed to the hospital. Her husband’s surgeon didn’t think he would survive the brain surgery.

It was only the beginning of what would be a series of brain surgeries, bouts with epileptic seizures, pneumonia, persistent fevers and continual pain that James Brady would suffer. His left leg and arm were paralyzed, and he would need the use of a wheelchair for the remainder of his life. His speech was slurred, and his short-term memory was damaged. At emotional moments, he would let out what Mrs. Brady called “the wail,” which she described as “a very unnerving noise somewhere between laughter and crying.”

He was released from the hospital after eight months. Home care and physical rehabilitation for her husband offered numerous unforeseen challenges for the Bradys. Mrs. Brady was both a mother and the manager of her husband’s complex medical care. The subject of gun control was years away.

In 1989, with Reagan’s presidency over and her husband out of the White House, Mrs. Brady was named chair of Handgun Control. In 1991, she became the chair of Handgun Control’s sister organization, the Center to Prevent Handgun Violence. In December 2000, the boards of Handgun Control and the Center to Prevent Handgun Violence voted to rename the two organizations the Brady Campaign to Prevent Gun Violence and the Brady Center to Prevent Handgun Violence.

She and her husband remained the public face of gun-control efforts well into the new century. Mrs. Brady noted it was always a struggle.

“The gun lobby never gives up,” she told the Times in 1990. “You get a good law, and they do everything they can to undo it.”