At 9:30 this morning, the nation observed a moment of silence to mark one week since the tragedy in newtown, connecticut. Church bells rang out, one for each victim and two more for the shooter and his mother. In washington, the president marked the moment, bowing his head in the oval ce. Within hours, another kind of silence was broken with the powerful national rifle association's defiant new message. Here's abc's senior justice correspondent, pierre thomas. Nra has blood on its hands. Shame on the nra! Reporter: The nra leader had barely begun when protesters blamed the powerful lobby for the nation's epidemic of gun violence. Nra, stop killing our children! Reporter: But the nra was defiant. After remaining silent in the wake of the worst elementary school shooting in the nation's history, wayne lapierre was on the attack blaming others for the recent carnage. High on the list, violent video games. There exists in this country, a callous, corrupt, and corrupting shadow industry that sells and stows violence against its own people. Reporter: Nra officials insist new laws restricting gun owners including a ban on assault rifles won't work. The primary solution the nra offers, armed security in every school. The only thing that stops a bad guy with a gun, is a good guy with a gun. Reporter: Critics pounced. The nra's blanket call to arm our schools is really nothing more than a distraction. Reporter: New york city mayor michael bloomberg called the nra statement a shameful evasion of the crisis. Earlier in an interview with abc news "nightline" anchor cynthia McFadden, bloomberg put some of the blame for gun violence at the feet of the gun lobby. The mayor wants what he calls reasonable restrictions, a ban on assault rifles and high capacity magazines. Our society finally has woken up and said, we are going to do this whether you like it or not. Reporter: As for putting armed security guards in schools some authorities support the concept of more police in -- there. But say there's no money to do so on such a huge scale. While the nra suggested some of the work could be done by volunteers, "the wall street journal" estimates it would cost $6.7 billion. And will it work? In some cases, perhaps. But at columbine, students were killed despite the fact armed police were there. Sfl two of the nation's biggest teacher's unions were sharply critical of the nra proposal, one saying the nra is delusional. Thanks, pierre.