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Alison and Andy Parker atop a Mayan pyramid in Mexico in 2013 in a photo he provided.

WASHINGTON — Until Wednesday, Andy Parker was a low-profile talent recruiter for small banks who also dabbled in politics and theater. Today, with his 24-year-old daughter having been gunned down on live television, he is the nation’s latest crusader for gun control.

“This is my life’s work,” said Mr. Parker, whose daughter, Alison Parker, was a news reporter at WDBJ in Roanoke, Va., before she and a cameraman, Adam Ward, were killed Wednesday by a disgruntled former colleague who also wounded Vicki Gardner, a woman being interviewed by Ms. Parker. “I’ve been robbed of a treasure that I will never see again, so the only thing I can do is make something happen where someone else’s treasure isn’t taken — and I’ll be damned if I’m going to stop.”

Mr. Parker, 62, who spoke in a telephone interview Thursday evening, has appeared on television extensively since Wednesday’s shooting, appearing composed, defiant — and often tearful — as he shares his new mission to fight the National Rifle Association, the nation’s leading champion of gun rights.

“I’m for the Second Amendment,” he said on CNN Thursday morning, “but there has to be a way to force politicians who are cowards in the pockets of the N.R.A. to make sensible laws to make sure crazy people can’t get guns.” Citing previous killings by people with mental illnesses, Mr. Parker asked, “How many Alisons will it take?”

But even as Mr. Parker made his impassioned pleas — and Gov. Terry McAuliffe of Virginia renewed his pledge to push for what he called “common-sense gun restrictions” — there was a feeling around the country that it would be as difficult as always for gun safety advocates to turn the killings in Roanoke into legislative changes.

Grief-stricken parents in other communities synonymous with tragedy — like Columbine, Colo., and Sandy Hook, Conn. — have made similar vows to change the system with little to show for their efforts.

“I hope this time will be different for us,” Mr. McAuliffe, whose package of gun control measures failed in the legislature this year, said Thursday in a telephone interview. “It’s like the hamster on the hamster wheel — you just go round and round, something happens, everybody comes out and says, ‘We need more gun restrictions,’ and then it fades into the background.”

President Obama learned that lesson in 2013 here in the nation’s capital, after the Senate defeated several measures to expand gun restrictions in the wake of the shootings in Sandy Hook that left 20 schoolchildren dead in December 2012. At the time, Mr. Obama called it a “pretty shameful day in Washington,” and this week, after the murders of Ms. Parker and Mr. Ward, 27, the White House showed little appetite to press for legislation again — even as Mr. Obama called the killings “one more argument for why we need to look at how we can reduce gun violence in this country.”

On the presidential campaign trail, gun control immediately became a partisan flash point between Hillary Rodham Clinton, the leading Democrat, and several Republicans. Mrs. Clinton called for “common-sense reforms to keep weapons out of the hands of criminals, the violently unstable, domestic abusers and even terrorists who find it pretty easy in our country to get ahold of weapons if they so choose.”

Republicans, including Donald J. Trump, the real estate mogul, and Gov. Chris Christie of New Jersey, suggested that such measures would have done little to prevent the deaths in Roanoke.

“This isn’t a gun problem; this is a mental problem,” Mr. Trump said.

In Virginia, where Mr. McAuliffe won election in 2014 despite an “F” rating from the N.R.A., he says he now intends to reintroduce the bills that failed earlier. The measures would restore a law restricting handgun purchases to one a month and require background checks for people to buy firearms at gun shows.

Mr. McAuliffe also vetoed two measures this year that would have expanded gun rights: one would have made it easier for Virginians to purchase machine guns, and another would have allowed residents to carry loaded shotguns and rifles in their vehicles.

It was unclear Thursday if the measures Mr. McAuliffe advocates would have kept the Roanoke suspect, Vester Lee Flanagan, from purchasing the Glock handgun he used to kill Ms. Parker and Mr. Ward. According to the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, Mr. Flanagan bought the gun at a “federal firearm licensee” in the Roanoke area within the past two months. He filled out an A.T.F. Form 4473, known as a “firearms transaction record,” and passed a standard background check, which in Virginia is conducted instantly by the State Police.

Proponents of gun rights were noticeably silent on Thursday. The N.R.A., which Mr. Parker singled out in his interviews, made no official statement, and its representatives did not return phone calls seeking comment.

But the shootings have galvanized advocates for gun control around the country — many of whom, like Mr. Parker, were spurred into activism after losing loved ones or becoming victims themselves.

“Some people are exhausted and have thrown up their arms and say, ‘I’m done, I just can’t do it anymore.’ ” said Patricia Maisch, who helped stop a 2011 massacre in Tucson that killed six and left a congresswoman, Gabrielle Giffords, gravely wounded. “But,” Ms. Maisch said Thursday, “I am not going away.”

In Virginia, a state with painful memories of the 2007 massacre at Virginia Tech, Lori Haas, whose daughter Emily was wounded there, struck a similar note. Mr. Flanagan, the Roanoke gunman, who died of a self-inflicted gunshot after he committed the murders, left behind a chilling manifesto in which he expressed admiration for the Virginia Tech killer.

“I feel a sense of optimism,” said Ms. Haas, who is today the Virginia state director for the Coalition to Stop Gun Violence, a national advocacy group. “As the frustration of the general public grows, the movement grows and the demands will grow, and our elected leaders will be booted out of office if they don’t do something.”

That was the message from Mr. Parker, the grieving father, who is no stranger to politics himself. He served four years on the Henry County Board of Supervisors after winning election in 2003 — and is now running again for his old seat, often introducing himself as “Alison’s Dad.”

On Thursday, as he made plans for a private celebration of life for his daughter, he said he had not given much thought to his own campaign. But he had a warning for politicians who oppose gun control: “I’m going to shame them, and embarrass them. My mission here is not to let this go away.”