Prominent gun rights advocates in the US government are now calling for a national discussion about curbing gun violence - signalling that the Connecticut primary school massacre could be a tipping point in a debate dormant for years.
White House officials said President Barack Obama would make preventing gun violence a second-term policy priority, but it was unclear what he would pursue or how and aides said stricter gun laws would be only part of any effort.
The president met his vice president Joe Biden and a handful of Cabinet members yesterday, including attorney general Eric Holder, education secretary Arne Duncan and health and human services secretary Kathleen Sebelius, to begin discussions on ways the country should respond to the Newtown shootings.
It remains to be seen whether Mr Obama and Congress can turn their rhetoric into action or whether the shock over the Connecticut shootings will fade before they do.
Public opinion has shifted against tougher gun control in recent years and the gun lobby is a powerful political force, particularly in Republican primaries.
Mr Obama has called for a national dialogue after other mass shootings during his presidency, only to see those efforts take a back seat to other pressing issues.
This time the president has vowed to use "whatever power this office holds" to safeguard American children against gun violence, suggesting he may put political muscle behind an assault weapons ban.
He has long supported reinstating the ban, which expired in 2004, but never pressed for in his first term. Liberal Democrats on Capitol Hill are already laying the groundwork for legislation to outlaw the military-style arms.
"Everything should be on the table," West Virginia senator Joe Manchin, a conservative Democrat, avid hunter and lifelong member of the National Rifle Association, said.
Republican senator Chuck Grassley of Iowa proposed a debate not just about guns but also mental issues.
And Virginia's Mark Warner, one of the few Senate Democrats who has found favour with gun rights groups, reversed course to back restrictions on assault weapons.
"The status quo is not acceptable any more," he said.
Democratic Senate majority leader Harry Reid vowed Congress would soon "engage in a meaningful conversation and thoughtful debate about how to change laws and culture that allow violence to grow". The Senate Judiciary Committee will hold hearings on gun violence early next year.
The American public has been split over tougher gun laws and there is no early indication that the Newtown shootings are changing many minds. A Washington Post/ABC News poll conducted over the weekend showed 54% favoured tougher laws, about the same as the 51% in favour earlier in the year. Seven in 10 are opposed to banning the sale of handguns to anyone except law enforcement officers, the highest percentage since 1999.
If Mr Obama follows through on his pledge to make the stemming of gun violence a priority, he is likely to press for a broad approach. He has previously called for improving mental health services for young people and instituting more effective policing strategies, though his rhetoric has never turned into a policy push.
He has said he believes the US constitution's Second Amendment guarantees an individual the right to bear arms and has spoken of a national heritage that cherishes hunting, shooting and the tradition of gun ownership. The president has signed laws letting people carry concealed weapons in national parks and in checked bags on Amtrak trains.
At the White House, press secretary Jay Carney said stricter gun control laws were part of the solution but not the only one. He said the president would engage in "the coming weeks" in a process that includes input from law enforcement, mental health experts and lawmakers.
"It's a complex problem that will require a complex solution," Mr Carney said. "No single piece of legislation, no single action will fully address the problem."
Democratic senator Dianne Feinstein said she would introduce legislation next year to ban the sale of new assault weapons, as well as big clips, drums and strips of more than 10 bullets.
Police say Newtown gunman Adam Lanza was carrying an arsenal of ammunition and used a high-powered rifle similar to the military's M-16.
Flanked by dozens of shooting survivors and relatives of victims of gunfire around the country, New York City mayor Michael Bloomberg said: "If this doesn't do it, what is going to?"
Such pleas have become near rituals for Mr Bloomberg, a billionaire who has used both his mayoralty and his own money to push the gun-control cause only to see it slide from the national agenda again and again. But he is pressing to make this moment a turning point.
Mr Bloomberg said yesterday that it was his place to speak out, saying "I'm a human being", as well as the mayor of the nation's largest city and one that he says is on track this year to log its lowest murder rate since record-keeping began in the 1960s.
"I'm going to fight, and you should fight, as well. ... This is an outrage. We are killing each other," he said.
Mr Bloomberg and the mayors' group he leads, Mayors Against Illegal Guns, are calling for reinstituting a version of the federal assault weapons ban that expired in 2004, by requiring all sellers to conduct criminal background checks on prospective buyers and stepping up prosecutions of people who lie on background checks.
Since the shootings, the powerful National Rifle Association lobby has been silent. Requests for comments have gone unanswered and officials are turning down interview requests until they have more details.
Their 1.7 million-strong Facebook group has disappeared and the group's Twitter account - a favourite platform to communicate with supporters - has not sent a message since before the grim reality of Friday's shootings set in.