A Connecticut official said the gunman's mother was found dead in her pajamas in bed, shot four times in the head with a.22-caliber rifle. The killer then went to the school with guns he took from his mother and began blasting his way through the building.
The tragedy plunged the picturesque New England town of 27,000 people into mourning.
"I know that Newtown will prevail, that we will not fall to acts of violence," said First Selectwoman Patricia Llodra. "It is a defining moment for our town, but it does not define us."
A White House official said Obama mainly wrote the speech himself. He worked with presidential speechwriter Cody Keenan, who helped Obama write his speech last year after shootings in Tucson, Ariz., left six dead and 13 wounded, including Rep. Gabby Giffords.
Just this past summer, Obama went to Aurora, Colo., to visit victims and families after a shooting spree at a movie theater in the Denver suburb left 12 dead.
In November 2009, Obama traveled to Fort Hood, Texas, to speak at the memorial service for 13 service members who were killed on the post by another soldier.
After the Colorado shooting in July, the White House made clear that Obama would not propose new gun restrictions in an election year and said he favored better enforcement of existing laws.
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