“I got out of the car and grabbed my rifle and it stopped for second,” Officer Chapman said. “But then we heard more popping. You could tell it was rifle fire. And it was up so close, it sounded like it was coming from outside. So we were all looking around for someone to shoot back at.”

As the officers converged on the building, the gunfire stopped again. Officers Chapman and Scott Smith made their way to the front entrance. It was here, only minutes earlier, that a rail-thin 20-year-old named Adam Lanza, armed with a .223 Bushmaster semiautomatic carbine, two semiautomatic pistols and hundreds of rounds of ammunition, had blasted his way through the glass.

Leonard Penna, a school resource officer who had raced to the scene from his office at the Newtown Middle School, entered the school with Sgt. Aaron Bahamonde and Lt. Christopher Vanghele, through a side door that leads to the boiler room, he said. Officer McGowan and two other officers entered through a locked rear door. One of them knocked out the glass with his rifle butt so the rest of the officers could get in.

The halls were familiar to Officer McGowan. He attended the school as a child. But now, they were eerily silent.

“The teachers were doing a phenomenal job keeping their kids quiet,” Officer Chapman said.

The officers turned their radios down. They entered the front lobby and saw the first bodies, those of Dawn Hochsprung, the principal, they would later learn, and Mary Sherlach, the school psychologist.

“You saw them lifeless, laying down,” Officer Penna recalled. “For a split second, your mind says could this be a mock crime scene, could this be fake, but in the next split second, you’re saying, there is no way. This is real.”

The officers went from room to room, urgently hunting for the killer before he could do more harm.

They found a wounded staff member in one room, made sure her co-workers were applying proper first aid and moved on.