"Evil visited this community today", Connecticut's governor told a nation traumatised by the slaughter of children. A tearful President Obama has promised "meaningful action" on guns.

Connecticut shootings: armed police on patrol (Reuters)

What drove Adam Lanza, aged just 20, to massacre 26 people, most of them young children, before turning the gun on himself? Another adult, believed to be his mother Nancy Lanza, has also been found dead.

The horror of what happened at the Sandy Hook elementary school in a quiet, ordinary town in Connecticut, is almost too great to comprehend. More than a thousand mourners gathered at a nearby church on Friday night, as the community struggled to deal with its grief.

"It was just brutal. I can't think of a better word. It was just brutal, to have to witness the pain today", the pastor, Monsignor Robert Weiss said after the service.

In a highly emotional address, frequently wiping away his tears, President Obama said America's heart was broken. "We're going to have to come together to take meaningful action to prevent more tragedies like this, regardless of the politics", he said.

In the immediate aftermath of the massacre, tens of thousands of people signed online petitions urging the White House to make good that promise, and calling for a new dialogue on gun controls. The largest had attracted more than 66,000 names by Saturday morning.

It was just brutal, to have to witness the pain today. Monsignor Robert Weiss

Political leaders have joined the calls for solutions, searching for something - anything - to prevent such tragedies from happening with such sickening regularity. Similar calls have followed other tragedies, like Columbine and Virginia Tech, yet nothing has changed.

On Friday, after White House spokesman Jay Carney suggested that now was not the time to talk about gun laws, activists insisted that the debate could hardly be more urgent.

"We say now is the time to talk about guns. Now IS the time to prevent more pointless deaths", declared a statement from Mayors Against Illegal Guns, whose chairman, New York's Michael Bloomberg, said simply calling for "meaningful action" was no longer enough.

"We need immediate action. We have heard all the rhetoric before", he said.

Congresswoman Carolyn McCarthy, whose husband was killed in a mass shooting in Long Island almost twenty years ago, has become one of the most vocal advocates of gun control in the house. "I hope the president's words about taking meaningful action to prevent more tragedies like this...stay true", she said.

She said she wanted concrete answers, and would be asking the White House exaxctly what they were planning to do.

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But the history of gun control legislation in the United States has not been an easy path: far from it, given the immense lobbying power of the main pro-gun organisation, the National Rifle Association, with its deep roots inside the Republican party.

The 1993 Brady handgun prevention act, named after the White House press secretary who was injured during the assassination attempt on President Reagan, introduced new background checks on gun owners and a number of restrictions on ownership, including a minimum age.

People will want to pass new laws, but unless you change peoples' hearts.. this is a heart issue. Laws don't change these kinds of things. Mike Huckabee

A year later, California senator Dianne Feinstein managed to steer an assault weapons ban through Congress, but at a price: a ten year limit, which expired under George W Bush with no attempt to renew it. Indeed, many Democrats attributed their steep losses in the 1994 mid-term elections to their support for gun controls.

A succession of opinion polls reveal little appetite for stricter controls, even in the wake of mass shootings. A Pew Research survey carried out after the Aurora movie theatre shootings in Colorado revealed that two thirds of those polled believed that such kilings were "just the isolated acts of troubled individuals", rather than a deeper problem with American society.

A divided nation

Offered a simple choice - guns, or no guns, most people opt for the former: Gallup found 73 per cent opposed to a ban on handguns, although pressed further, many people would opt for more specific restrictions.

Now, though, the sheer awfulness of what happened in that Newtown school may prompt a more universal response, as gun control campaigners hope. Marion Wright Edelman, from the Childrens' Defence Fund, spoke for most: "How many children need to die before we stop the proliferation of guns in our nation?"

On the Republican side, there have been no calls for sweeping new legislation, but a genuine grief: House Speaker John Boehner urging the nation to unite: "for that is how Americans rise above unspeakable evil."

Others on the right warned against enacting new laws before a more careful deliberation. Former Arkansas governor Mike Huckabee said a kneejerk response would be futile: "People will want to pass new laws, but unless you change peoples' hearts.. this is a heart issue. Laws don't change these kinds of things", he told Fox News.

President Obama has shied away from any action on guns in the past, fearful of alienating more white working class voters. But now all that could change: with the president under huge pressure to act. This is, after all, his second term: no worries about re-election.

Now is precisely the time not just to talk about gun control, say activists, but to take action. For in a nation which has by far the highest number of gun-related deaths in the world, if not now, then when?

Felicity Spector writes about US politics for Channel 4 News