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Shooter Adam Lanza forced his way into Sandy Hook Elementary School and went on to shoot 26 students and staff members on Dec. 14, 2014.

A school secretary who caught a shadowy glimpse of someone carrying a rifle, a janitor who heard booming gunshots, a teacher sheltering her students behind an unlocked door — these were among the first 911 calls alerting dispatchers that something was terribly wrong inside Sandy Hook Elementary School.

Police 911 recordings of the Dec. 14 massacre that were made public Wednesday by Newtown, Conn., officials reveal a school under siege.

Audible gunshots ring out on several tapes as emergency operators are heard urging callers to take cover and stay quiet.

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The first quavering call came in at 9:35 a.m., moments after deranged killer Adam Lanza, armed with an AR-15 assault rifle, blasted his way through the school’s glass front door.

“I think there’s somebody shooting in here in Sandy Hook school,” says the woman, a secretary in the central office who has been identified by local newspapers as Barbara Halstead.

“What makes you think that?” the dispatcher responded.

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“Somebody’s got a gun, I saw a glimpse of somebody running down the hallway. Oh, they’re still around me, there’s still shooting,” Halstead said, her voice rising in fear and shock.

A minute later, at 9:36 a.m., custodian Rick Thorne called to say he heard shots fired.

“Something’s happening,” he said, identifying himself for the dispatcher, who can be heard turning to a colleague and ordering her to “get everyone you can going down there.”

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“There’s still shooting going on! Please!” Thorne said. Another cluster of gunfire erupted, and he can be heard saying, “Still, it’s still going on!”

At 9:37 a.m. a young woman who said she was a teacher at Sandy Hook dialed 911.

“It sounds like there are gunshots in the hallway,” the unidentified teacher said with forced calm, adding that her students were with her.

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“I have to go lock the door,” she told the dispatcher.

Lanza killed six female staffers and 20 children — all between 6 and 7 years old — within minutes of entering the school. He shot himself as police arrived on scene. Eleven grim minutes had elapsed.

The 20-year-old gunman shot his mother Nancy Lanza at their home before heading to the school.

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The seven, audio-enhanced recordings were made public Wednesday against the wishes of local authorities, who said the tapes would bring unnecessary pain to the Newtown families.

But Connecticut Superior Court Judge Eliot Prescott last week ordered them released, dismissing the argument that the shooting was a case of child abuse and the calls equivalent to signed witness statements.

Calls that were routed to state police are still not public, pending a freedom of information request by The Associated Press.

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The Newtown police arrived at the school within four minutes of the first 911 call, according to a state report released last week.

They waited outside for nearly six minutes while trying to figure out if there was a second shooter.

Lanza killed himself with a Glock pistol about one minute after cops arrived, records show.

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