Investigators assembled “some very good evidence” to explain what drove a 20-year-old gunman to slaughter 20 children and six adults at an elementary school, police said on Saturday, a day after one of the worst mass shootings in U.S. history shattered a small Connecticut town.

The attacker, identified by law enforcement sources as Adam Lanza, opened fire on Friday morning at Sandy Hook Elementary School in Newtown, which teaches children aged 5 to 10. The shooter killed 26 people – including first-graders, who would be about 6 years old – before turning the gun on himself.

He was also suspected of killing another person, possibly his mother, before the massacre.

“Our investigators at the crime scene … did produce some very good evidence in this investigation that our investigators will be able to use in, hopefully, painting the complete picture as to how – and more importantly why – this occurred,” Connecticut State Police Lieutenant Paul Vance told a news conference.

The shooting has tormented the town of Newtown, once listed as the fifth-safest city in the America but now in crisis.

“This recovery is going to be not a sprint but a marathon. It’s going to be a long process,” said U.S. Senator Richard Blumenthal of Connecticut.

Yale-New Haven Hospital opened a crisis-intervention center in the wealthy suburb of 27,000 people about 80 miles from New York City. By mid-morning, about 50 cars were parked outside. A sign warned media to stay away.

The tragedy moved President Barack Obama to tears on national television on Friday and rattled a country that has grown accustomed to mass shootings, but not with victims so young. It also stood to revive a debate about U.S. gun laws.

Obama, in his weekly radio and Internet address on Saturday, called for “meaningful action to prevent more tragedies like this,” but stopped short of specifically calling for tighter gun-control laws.

“The kids who died were in two first-grade classrooms (6-year-olds),” said Mary Ann Jacob, a school library clerk who described leading children out of danger during the shooting.

‘EVIL IS A CHOICE’

About 50 people gathered for a service at St. John’s Episcopal Church in the neighboring town of Sandy Hook to remember the victims, ending the service by singing the hymn “Amazing Grace.”

“Evil is a choice. It does not come from God,” the Reverend Mark Moore said in his sermon. “Even though evil can overcome us, it cannot overcome God.”

“In the end, all will be well,” he said, and the people responded with a loud “Amen.”

Afterward, Mary Fellows, 49, a life-long resident of Sandy Hook, said she went to the service to try to find peace while waiting to discover if she knew any of the victims. “Even if you didn’t know their names, you know their faces,” Fellows said.

The National Shooting Sports Foundation headquarters sits just up the street from the grief center. White holiday candles had been placed in its back windows. A security guard shooed away any visitors.

Vance, the police spokesman, declined to describe the evidence gathered about the shooter’s motives but did say the gunman forced his way into the school.

Crime-scene investigators worked through the night and moved the bodies to the state medical examiner’s office for autopsies, police said in a statement. Victims’ names had yet to be released.

The woman found dead at the secondary crime scene was related to the shooter, a police news release said. Many media outlets have reported she was the shooter’s mother, Nancy Lanza.

Nancy Lanza legally owned a Sig Sauer and a Glock, both handguns of models commonly used by police, and a military-style Bushmaster .223 M4 carbine, according to law enforcement officials who also believe Adam Lanza used at least some of those weapons.

“We’re investigating the history of each and every weapon, and we will know every single thing about those weapons,” Vance said.

Nancy Lanza was an avid gun collector who once showed him a “really nice, high-end rifle” that she had purchased, said Dan Holmes, owner of a landscaping business who recently decorated her yard with Christmas garlands and lights. “She said she would often go target shooting with her kids.”

Newtown was ranked the fifth safest city in America by the website NeighborhoodScout.com based on 2011 crime statistics.

“This wonderful town that we all love for its peace, beauty, the great schools – all of that – has become Columbine,” said Julie Maxwell Shull, a sixth-grade teacher at Reed Intermediate School, referring to the high school that was site of a 1999 shooting in Colorado.

The holiday season tragedy was the second shooting rampage in the United States this week and the latest in a series of mass killings this year.

In another incident, Oklahoma police arrested an 18-year-old high school student on charges that he was plotting to carry out a shooting and bombing massacre at his school, according to the Tulsa World newspaper.

Police said in an affidavit Chavez tried to recruit other Bartlesville High School students to help him lure classmates into the school auditorium, where he planned to chain the doors shut and start shooting them, the newspaper said.

The Connecticut massacre revived a debate about gun-control in a country with a flourishing firearms culture and a strong lobby that has discouraged most politicians from any major efforts to address the easy availability of guns and ammunition.

The death toll exceeded that of one of the most notorious U.S. school shootings, the 1999 rampage at Columbine High School in Littleton, Colorado, where two teenagers murdered 13 students and staff before killing themselves.

(Reuters)