A key piece of my post on the horror at Sandy Hook Elementary School on Friday turned out to be wrong: Adam Lanza did not enter the kindergarten classroom where his mother taught. She had no connection to the school. She wasn’t even there when he killed her. Now that we know Lanza murdered his mother at home then shot his way into the school only compounds the disbelief and revulsion of such an unfathomable act.

Nor were the children Lanza murdered between the ages of 5 and 10 years old, as we first thought. As the front page of Sunday’s Post and New York Times made dramatically clear, most of Lanza’s targets were just 6 and 7 years old. That they sustained multiple wounds, that Lanza had a semi-automatic weapon, two handguns and hundreds of bullets at the ready, that he stopped to kill himself only upon hearing the approach of first-responders broadens the scope of this tragedy far beyond our fears.

E. J. Dionne is right: This time has to be different. Yes, President Obama must lead on this issue. But his voice must be the loudest among many. Whatever action he takes must be backed up by a Congress unshackled from its bipartisan fear of the National Rifle Association. This is where Michael Bloomberg comes in.

In the blunt-spoken mayor of New York City, we have an anti-illegal guns advocate who is unafraid to take on the NRA. That he is a billionaire gives him the financial power to put his money where his mouth is and to attempt to match the financial power of the NRA. Said billions also give Bloomberg the independence to tell the gun lobby to stuff it. This year he started Independence USA PAC, a super PAC that has as one of its goals electing members of Congress who will crack down on illegal guns. Mayors Against Illegal Guns is a Bloomberg creation that now has a coalition of more than 700 mayors from across the country.

Oh, Bloomberg hasn’t been shy about slamming Obama and other elected officials who haven’t used their power to make us safer from gun violence. But now it’s time for all of us to join in the effort.  There is a right to bear arms, but no right is absolute. So, when an elementary school is no longer sacrosanct, the laws must change. As @stone_circle tweeted late Sunday afternoon, “Guns are not SACRED. Children ARE.”

“We can’t tolerate this anymore. These tragedies must end. And to end them, we must change,” the president said last night in Newtown, Conn. “We will be told that the causes of such violence are complex, and that is true. No single law, no set of laws can eliminate evil from the world or prevent every senseless act of violence in our society, but that can’t be an excuse for inaction. Surely we can do better than this.”

Yes, we can. Yes, we must. It starts with him. It continues with us.