The chilling story behind this photo of men, women and children sunbaking.

A series of photos taken between May and December 1944 depict a group of men, women and children enjoying themselves at what appears to be a resort.

They’re smiling, laughing, eating, listening to music and socialising – as many people do over the warmer European months.

Here, a group of men and women laugh as one man plays the accordion:

In another photo, people relax on sunbeds.

In yet another, a smiling man plays with his dog.

Taken together, the images appear to tell a story of a happy group of people on holiday. But this assumption couldn't be further from the truth.

The photos belong to a gallery titled, 'Laughing at Auschwitz,' which shows officers and guards at Auschwitz relaxing and enjoying themselves just kilometres away from the death camp.

They smile and listen to music and play with their children and pets while countless people are being murdered just moments away. And they seem completely oblivious.

These are some of the very few photos that exist of 'leisure time' of the concentration camp's SS officers, and they elicit a strong visceral response.

Watch: The horror of Auschwitz. Post continues after video. 

The United States National Holocaust Museum in Washington made the photos public after obtaining them from a US officer who found them in an apartment in Frankfurt. In a statement, the museum's director, Sara Bloomfield powerfully articulated what makes these images so chilling.

"These unique photographs vividly illustrate the contented world they enjoyed while overseeing a world of unimaginable suffering," she said. "They offer an important perspective on the psychology of those perpetrating genocide."

Judith Cohen, the director of the museum’s photographic reference collection, said "precisely what makes [the photos] so horrible" is the fact that they don't show anything confronting or heinous. These people appear "normal" - their faces aren't the faces of killers.

The album was found to belong to Karl Höcker, the man pictured playing with his dog. He was an SS commander and adjutant to the commander of Auschwitz concentration camp. In 1963, Höcker stood trial for his crimes at Auschwitz, and said, "I had no possibility in any way to influence the events and I neither wanted them to happen nor took part in them."

Listen to Magda Szubanski reflect on her family's Holocaust story. Post continues after audio.

"I didn’t harm anyone and no one died at Auschwitz because of me."

Ultimately, he spent seven years in prison for aiding the murders of 1,000 Jews.

The most well-known individual photographed is Dr. Josef Mengele, who became known as the 'Angel of Death' for the he tortured those at the death camp, conducting horrific medical experiments. He exposed children to surgeries with no anesthesia, injected chemicals into their eyes in an attempt to change their eye colour, and removed the limbs and organs of twins in archaic surgical procedures.

Here, he takes a break with fellow officers:

The images convey the chilling apathy of those carrying out unimaginable horrors - and remind us of the potential for terrifying outcomes when prejudice and racism prevail in any society.