Rainer Hoess was 15 years old when he realized his family had secrets — enormous, dark secrets.

A young boy in Germany at the time, he was on a school trip to the Dachau Concentration Camp when he stumbled across informational placards talking about a Nazi officer with the same last name as his.

The officer wasn't just a rank-and-file Nazi. He was Rudolf Hoess, commandant of the Auschwitz death camp for five years.

"He was a million-mass-murderer in the Second World War, without regret or remorse in any way," says Hoess, who was in Toronto speaking to high school students as part of Holocaust Education Week.

"I think it's so strong and powerful for him to speak to so many people about such a sad experience," says Sibyl Martasna, a student who heard Hoess' presentation at Northern Secondary School in Toronto.

SS-Obersturmbannfuhrer Rudolf Hoess is seen in Warsaw on March 11, 1947, the first day of his trial for war crimes committed at Auschwitz concentration camp, of which he was the first commandant. He was sentenced to death and hanged on April 16. (Keystone/Getty Images)

It was Hoess' grandfather who ordered the use of Zyklon B gas to increase the number of people who could be executed at Auschwitz, with that number reaching as high as 2,000 killed each day.

In all, more than one million people, mostly Jews, were murdered at Auschwitz during Rudolf Hoess' tenure.

He eventually was captured and admitted to his crimes at the Nuremberg Trials after the Second World War, and was hanged at Auschwitz.

"I grew up with the understanding that my family had lived through the terrors of the Nazi occupation in the Netherlands," his grandson says. "Nothing in these stories prepared me for the weight of our true experience at Auschwitz."

This photograph, taken just after the liberation by the Soviet army in January 1945, shows a group of children in the Auschwitz concentration camp. (Associated Press)

As a teen, after confronting his father with the stark discovery about his grandfather, Rainer Hoess says he was met with more denials. He did his own research, and eventually understood the truth.

He left home and cut all ties with his family.

Since then, he has dedicated his adult life to talking about his family's past, and supporting holocaust survivors in an attempt to combat hate in all its forms.

"Right now, I'm 54 years old and I'm still in the process of separating myself from the family, it's a long-lasting process," says Rainer Hoess, who has no idea if his father is even still alive.

"These are the steps in my life I took to get out of the shadow of my grandfather … I found my way to deal with it is to go to schools and talk, around 80 to 100 schools a year."

In addition to speaking to students, Hoess started a website called Footsteps to create awareness about his family's past. The stories he has uncovered are chilling.

His father, Hans-Juergen Hoess, was one of Rudolf Hoess' five children and lived on the grounds of Auschwitz with his family while his father ran the camp.

The family had a vegetable garden outside their home, and Rainer Hoess recounts how his grandmother would warn the children to rinse anything before eating it to ensure the ashes were washed off — they were the human ashes from the crematoria overlooking their home.

Crematory and gas chamber IV, seen in this 1943 photo taken by the German SS, was one of the buildings where Auschwitz prisoners were executed and cremated. (Auschwitz-Birkenau State Museum Archives)

Rainer also found rings belonging to his grandfather, made from the gold fillings of hundreds of Jewish prisoners.

He tells these stories over and over to groups of people in the hopes that they understand the horrors of the past and do not allow them to be repeated. He says that's what keeps fuelling his life's work.

"The point is to prevent something like that ever happening again," he says. "We live in a really brutal and cruel world. I mean, just look at what happened in Pittsburgh or right now in Germany ... everywhere where crimes are committed against Jews, Muslims, homosexuals, it's hate," he says.

Prisoners from the Auschwitz concentration camp were used as forced labour by the Nazis. (Auschwitz-Birkenau State Museum)

Organizers who brought him to speak in Toronto understood the message would carry a lot of weight coming from the descendant of a figure like Rudolf Hoess.

"I think for Jews to tell the message of combating hate and anti-Semitism is really important, but I think coming from somebody with that family background, somebody who was raised by people who were essentially Nazis — that's really compelling for students to hear, it makes it very real," says Dara Solomon, of the Sarah and Chaim Neuberger Holocaust Education Centre.

Ace Chou, another student from Northern Secondary School, was clearly affected by Hoess' talk. "I think it's really brave of him, and it is definitely necessary for people to learn about the history," he says.

Rainer Hoess shows the picture of his family on the cover of his book 'The Legacy of the Commandant.' (Jonathan Nackstrand/AFP via Getty Images)

Hoess has gone further than just speaking to students. He has visited Auschwitz more than 30 times, taking groups back to see his grandfather's former home there and the camp he ran.

He has made personal contact with more than 70 holocaust survivors and created close relationships with many of them. One, Eva Mozes Kor, even adopted him as her own son before she passed away last year.

And, in 2013, he wrote his family's story in a book titled The Heritage of the Kommandant: On being part of a terrible family, to make sure future generations don't forget the horrors of the past.

"An obsession really became a passion for me with this work," says Hoess.

"As long as I can, I will do this work — as long as my feet go one in front of the other."

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