The National Shooting Sports Foundation, the gun manufacturers' trade group, which is headquartered in Newtown, the town where the killings occurred, said in a statement: "Our hearts go out to the families of the victims of this horrible tragedy in our community."
The foundation, which runs the country's largest trade gun show in Las Vegas each year, said it would have no further comment "out of respect for the families, the community and the ongoing police investigation."
Adam Lanza walked into the school where his mother taught with two handguns, a Glock and a Sig Sauer, according to law enforcement officials. Lanza also possessed a .223 Bushmaster rifle, a semiautomatic assault weapon, but it still is unclear whether he brought it into the school.
Six adults were shot dead at the school. Another body, believed to be Lanza's mother, was found at a house in Newtown.
A law enforcement source said Lanza possibly obtained the weapons from a family member. He fired "dozens and dozens of shots," said another law enforcement source.
The Glock is serially employed in mass shootings: It was used in the Tucson shooting, at the 2007 Virginia Tech shooting that killed 32 people and wounded 27 others, and at the movie theater shooting in Aurora, Co., in July that left 12 people dead and 58 wounded at the midnight show.
The Sig Sauer was used in a 1989 shooting in Louisville, Ky. that left eight people dead and 12 wounded. And the Bushmaster was the weapon used by snipers John Allen Muhammad and Lee Boyd Malvo, who terrorized the Washington metropolitan area in 2002, killing 10 people and critically wounding three.
President Barack Obama said Friday that "we're going to have to come together and take meaningful action to prevent more tragedies like this, regardless of the politics."