NEW YORK — "Newtown 911, what's the location of your emergency?"

The voice on the other end shook with fear.

"Sandy Hook school," the woman said. "I think there's somebody shooting in here."

It was the first call received by police in Newtown, Conn., the morning of Dec. 14 after Adam Lanza had shot his way into the elementary school and begun rampaging down the corridors and into classrooms.

When he was done, 20 first-graders and six school employees lay dead.

Lanza, 20, who had shot his mother, Nancy, to death in their Newtown home, then killed himself.

Nearly a year after the massacre, detailed records of the police investigation and some of the 911 calls have been made public, despite efforts by many in Newtown and Connecticut to keep them sealed. Families of most victims contended that putting details of the horrible day in the public domain would only make it more difficult to recover from their loss.

LISTEN: Dramatic 911 calls

The state last month released a 48-page summary of the police report, which revealed Lanza's obsession with mass murders, his antisocial behavior and the easy access to weapons he had in his mother's home. But the report did not shed light on why Lanza targeted Sandy Hook Elementary School.

Last month, a judge ruled that the state's Freedom of Information Act mandated that the 911 calls made to Newtown police be released, and he ordered it done by Wednesday. At 2 p.m., police posted the recordings online, revealing both the terror of the morning and the calm demeanor of police dispatchers who tried to reassure callers as gunfire echoed through the halls.

"Somebody's got a gun. I caught a glimpse of somebody," the woman who made the first call said anxiously to the 911 dispatcher as the rampage began.

"They're running down the hall. They're still running, they're still shooting," she said before pleading again for police to come. "Sandy Hook school, please."

By then, police were juggling calls from others in the school and from friends and relatives of people who worked there. One man called to say his wife had texted him from Sandy Hook that there was a shooting. A young woman said she had a friend at the school. "I hope she's OK," she said when a dispatcher assured her that police were on their way.

All of them knew something was wrong, but nobody knew exactly what was happening.

"I believe there's shooting at the front glass. Something's going on," the school's custodian, Rick Thorne, told police after Lanza shot out the windows near the school's locked front door to gain entrance.

Thorne said the school was locked down and all the children were in classrooms, but he remained in a corridor, even as the sound of gunfire became clear over the phone.

"I'm close," he told the dispatcher, who told him to "take cover."

"I keep hearing shooting," Thorne said. "I keep hearing popping."

PHOTOS: Newtown school shooting

In Room 1, a teacher who had been shot in the foot called in. There were children huddled in the room with her and two other adults.