Last month, Newtown, Conn. suffered one of the most devastating mass shooting in United States history when Adam Lanza shot 20 elementary school students and six school staff members. The first people to respond to 911 calls were law enforcement officers from the Newtown community and what they saw has changed them forever.

This is how the scene was described in a PoliceOne article:

The gunfire ended; now it was so quiet they could hear broken glass and bullet casings scrape under their boots. The smell of gunpowder filled the air. The officers turned down their radios: if there was still a shooter, they did not want to give away their position.

They found two women first, their bodies lying on the lobby floor. This was real. But nothing could prepare them for what they found next, inside two classrooms.

”One look, and your life was absolutely changed,” said Michael McGowan, one of the first police officers to arrive at Sandy Hook Elementary School on Dec. 14, as a gunman, in the space of minutes, killed 20 first-graders and six adult staff members.

According to the PoliceOne article, many of the officers are still knee-deep in the process of reconciling what they saw that day. “Some spoke reluctantly, not wanting to compare their torment with the agony of the families of the victims,” the article stated. “But they also worried about their ability to do their jobs.”

The sight of the victims isn’t the only thing lingering in officers’ minds. Detective¬†Jason Frank said it was the little things like the unfinished Christmas ornaments and backpacks strewn about.

”It’s heartbreaking,” he said. ”These kids will never take those ornaments home to their parents.”