Francisco Boix, a Spanish photographer, stole photos that were used as evidence in Nuremberg. It marks the 70th anniversary of the camp's liberation.

Francisco Boix, a Spanish photographer, stole photos that were used as evidence in Nuremberg. It marks the 70th anniversary of the camp's liberation.

Prisoners photographed by the camp's Identification Service, where Francisco Boix worked. Some 200,000 prisoners of various nationalities passed through Mauthausen, liberated by the US Army on May 5, 1945, and other concentration camps dependent on it, such as Gusen. Half died, including 4,761 of the 7,200 Spanish Republicans who were confined there.

A group of prisoners tear down the Nazi symbol installed at the entrance to the Mauthausen camp on the day of liberation. Spanish photographer Francisco Boix documented the first hours after the Nazis escaped.Francisco Boix

Another moment of the demolition of the Nazi symbol installed at the entrance to the Mauthausen camp, on the very day of liberation.Francisco Boix

Photograph taken on the day of the liberation of Mauthausen, showing hundreds of dead in the Nazi camp. Boix didn't just take his own images. His greatest contribution was the theft, thanks to his work in the photo lab, of thousands of negatives depicting life and death in the camps, which the Nazis had ordered to be destroyed.Francisco Boix

A Mauthausen prisoner died at one of the Nazi camp's electrified fences. With the help of other Spanish prisoners and Anna Pointner, a resident of Mauthausen, Francisco Boix managed to smuggle thousands of negatives out of the camp, which served as evidence at the Nuremberg trials.Francisco Boix

Hundreds of naked prisoners awaiting general disinfection at Mauthausen, June 21, 1941.Francisco Boix

Mauthausen quarry staircase, with 186 steps, where hundreds of prisoners lost their lives. According to Francisco Boix, the camp's history estimates one dead man for each step.Francisco Boix

Francisco Boix, with a Nazi camera and an armband identifying him as a Spanish war reporter, shortly after the liberation of Mauthausen, on May 5, 1945. The communist photographer died in 1951 in Paris from the after-effects of his captivity.