"It's incomprehensible, the pain here," Darla Henggeler said. "You can't imagine. We're still in shock. I can't let my heart go there because it's so overwhelming.

"Once it settles in, I think my heart will break."

Ex-school official: Lanza would 'withdraw into his own little world'

When he was the Newtown public schools' director of security, Richard Novia knew Adam Lanza. In high school, the then-teen had psychological issues and would sometimes "withdraw into his own little world," Novia said.

But he never saw Friday's carnage coming.

"I interacted with that boy daily for several years," Novia told Nancy Grace from HLN, CNN's sister network. "And I can tell you that there was no indication he would carry out a heinous act."

Lanza worked with Novia in Newtown High's Tech Club, with his mother -- who the former security director described as "doting" and very involved in her children's lives -- often taking part in its activities. She'd also be called to the school when Adam Lanza "would have little episodes ... where he could not ... talk or communicate, even what he was feeling."

Citing local school authorities, Vance said Monday there was "no connection" between the shooter and with the elementary school he targeted. Cynthia Jaroszewksi, though, told CNN that Lanza once attended that school and was even in the same first- and third-grade classes as her daughter, Rebecca.

No class for Sandy Hook students 'until further notice'

As to Sandy Hook's current students and faculty, they will be out of school "until further notice," Newtown Police Lt. George Sinko said.

When classes do resume, it will be in a different place.

Authorities have said Sandy Hook students and staff will be at Chalk Hill Elementary in neighboring Monroe, Connecticut, with Gov. Dannel Malloy saying he's signed an order to expedite such a move. In fact, moving trucks were parked outside the Newtown school Monday, to transport supplies and equipment to their home.

School will be in session for other students in town Tuesday, albeit after a 2-hour delay.

"Be assured that the safety of your children and our staff are our first priority," Superintendent Janet Robinson told parents in an e-mail. "(Police) Chief (Michael) Kehoe along with his colleagues from the State Police and surrounding communities are implementing a security plan which will provide increased presence at all of our schools."

Massacre stirs debate about gun control

Preventing future Newtowns isn't just on Connecticut residents' minds. The massacre has spurred talk nationwide about gun violence and how to prevent it.

President Barack Obama's call for change was the centerpiece of his address Sunday night at Newtown High School. Referencing other mass shootings over the last two years, he said Americans can't "honestly say we're doing enough to keep our children -- all of them -- safe from harm."

To that end, Obama promised, "In the coming weeks, I will use whatever power this office holds to engage my fellow citizens -- from law enforcement to mental health professionals, to parents and educators -- in an effort aimed at preventing more tragedies like this."

While gun rights groups like the National Rifle Association have been largely silent since Friday's shooting, others have spoken up.

Malloy, Connecticut's governor, said Monday, "I'd love to hear the people argue that we need 30-round magazines and that's somehow tied to the right to bear arms. We're not talking about basic weapons that are used in hunting."