Undated photo of Adam Lanza, who killed himself after fatally...

Undated photo of Adam Lanza, who killed himself after fatally shooting 27 people, including 20 schoolchildren, at a school in Newtown, Conn., on Dec. 14, 2012. (Dec. 31, 2012) Credit: NBC 4 NY

The 20-year-old gunman shot his way into Sandy Hook Elementary School carrying hundreds of bullets, firing multiple times at each of his 26 victims, then killing himself with a handgun as authorities were closing in, officials said Sunday.

Adam Lanza, who forever changed the history of this quiet New England town, had shot his mother, Nancy Lanza, in the face at their home before driving her car to the school on Friday, police said.

Connecticut Gov. Dannel P. Malloy said Lanza killed himself as first responders were closing in on him. Investigators say the children were killed in two separate classrooms.

"We surmise that it was during the second classroom episode that he heard responders coming and apparently at that, decided to take his own life," Malloy said on ABC's "This Week."

Investigators are still interviewing witnesses and would not give any indication as to a motive. But Connecticut State Police Lt. J. Paul Vance said he was confident questions about the second-worst school shooting in the United States would ultimately be answered.

He said all of the victims at the school, including 20 first-graders and six adults, were shot with a Bushmaster AR-15 assault rifle and that "numerous" magazines were emptied at the scene. Lanza, a quiet young man described as developmentally disabled and who struggled socially, had hundreds of bullets that went unused, Vance said.

"There was a lot of ammo, a lot of clips," he said. "Certainly a lot of lives were potentially saved" by first responders approaching the school.

Detectives executed several search warrants at Lanza's home and have seized a lot of evidence, Vance said, but he would not elaborate on what they found.

Phoned-in threat to churchAs the community mourned Sunday, they turned to churches and each other for comfort and support. St. Rose of Lima Roman Catholic Church hosted three packed Masses in the morning. In the afternoon, however, the building was evacuated because of a phoned-in threat, police said.

The rectory and church were scoured by law enforcement officials, their weapons drawn. Vance would not provide details about the nature of the call.

Such threats and any social media "misinformation" that is "threatening" and "inaccurate" will be investigated and anyone creating or sending such information would be prosecuted, he said.

On some social media outlets, including Facebook, postings purport to come from Lanza.

"It is important to know that we have discussed with federal authorities that these issues are crimes," Vance said during a news conference. "They will be investigated statewide and federally and prosecution will take place when people perpetrating this information are identified."

The State Police have 250 troopers investigating the shootings and Newtown Police Department detectives, ATF, FBI, the Connecticut forensic laboratory and municipal agencies are all assisting. Vance called the group "the best of the best."

The weapons uncovered, including a shotgun in Lanza's car parked at the school, are being traced "back to the workbench where they were being assembled," he said.

"I am confident we will put every single resource we have into this investigation and will answer every question possible by the conclusion of this case," Vance said.

Law enforcement officials said Lanza visited an area shooting range but they have not concluded whether he actually practiced there, The Associated Press reported. Ginger Colburn, a spokeswoman for the Bureau of Alcohol, Tobacco and Firearms, would not identify the range or say how recently he was there.

Lanza's mother visited shooting ranges several times but it's not clear if she took her son or if he'd ever fired a gun there, Colburn said. The AP reported that Lanza's mother was shot four times while dressed in her pajamas.

Nancy Lanza, 52, owned guns for self-defense, her former sister-in-law, Marsha Lanza, of Crystal Lake, Ill., told CNN, although "she never felt threatened, or she would have said something."

The weapons found at the scene of the shooting were legally purchased by Nancy Lanza, CNN reported.

At Newtown High School, Adam Lanza would have crises that only his mother could defuse, a family friend told the AP.

"He would have an episode, and she'd have to return or come to the high school and deal with it," said Richard Novia, the school district's head of security until 2008, who got to know the family because both Lanza sons joined the school technology club he chartered.

With Adam Lanza, it "wasn't a rebellious or defiant thing," Novia said. "It was withdrawal."

Police say the shootings took place in a single section of the school, including classrooms and a hallway, but would not say specifically where the bodies were found.

Newtown police Lt. George Sinko said it's unclear whether the surviving students will ever return to the campus.

"It's too early to say, but I would find it very difficult for them to do that," he said, adding that children might be moved to another school.

While police continue their investigation and schools around the country assess their safety, local, state and federal elected officials are calling for another look at stricter gun control laws. But such debates offer little relief to a struggling community.

Nancy Elis, 66, lives 10 minutes from Newtown and visited Sunday to connect with local residents. She was still stunned Sunday by the violence at the school and by the new threat against the church.

"You don't see that in a little town like this," she said. "You see it on television, you see it in a big city environment, you see it in a war zone, you don't see it here. It just feels so wrong."

With Tania Lopez, Nicholas Spangler, Patrick Whittle, Candice Ruud, Lauren R. Harrison and Bill Bleyer

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