Holocaust denier Ernst Zundel has died in Germany of an apparent heart attack, according to his wife, Ingrid Zundel. He was 78 years old.

Zundel, who immigrated to Canada in 1958 and lived in Toronto and Montreal, was extradited to Germany in 2005 and served a five-year prison for inciting hatred.

Zundel was famously convicted in 1985 under section 181 of the Criminal Code of Canada for “knowingly publishing false news,” after he published a brochure called "Did Six Million Really Die?” The conviction was overturned and later deemed unconstitutional by the Supreme Court of Canada.

Ingrid Zundel said in a statement to CTV News that her husband died in his childhood home in the Black Forest.

“Details are still sketchy, but I know that his sister, Sigrid, was with him when it happened,” she wrote. “She found him unconscious and called the ambulance. He was pronounced dead shortly thereafter,” she added. “Apparently it was a heart attack.”

Zundel, who lives in the United States, added that she spoke to her husband "just hours before he passed on and he was as optimistic and upbeat as ever."

With files from The Associated Press