Nikolai Volkoff, real name Josip Nikolai Peruzović, best known as the evil Russian who teamed up with The Iron Sheik to become a World Tag Team Champion, has died. He was 70.

“WWE is saddened to learn that Josip Nikolai Peruzović, known to WWE fans as Nikolai Volkoff, has passed away at age 70,” WWE said in a statement. “WWE extends its condolences to Peruzović’s family, friends and fans.”

“MY BEST FRIEND,” the Iron Sheik, real name Hossein Khosrow Ali Vaziri, tweeted Sunday morning. “MY PARTNER. MY BROTHER. WE GET MORE HEAT THAN ANYONE ON EARTH. I TRUST HIM WITH MY LIFE. HE TAKE CARE OF ME WHEN I WAS DOWN. I MISS YOU FOREVER ??'”

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Other professional wrestlers took to Twitter to pay tribute to the legendary heel, with James Ellsworth writing, “I did many road trips with Nikolai Volkoff. As we only lived 15 minutes from each other. I learned so much from him. He was one of the kindest people I’ve ever met. I’ll miss him dearly #RIPNikolaiVolkoff”

“Sad to hear the passing of @WWE Hall of Famer Nikolai Volkoff,” Tommy Dreamer tweeted. “Celebrate his life… Watch his greatness on @WWENetwork and all please rise as he sings the Russian National Anthem.”

“I always loved our conversations backstage …,” Natalya “Nattie” Neidhart added. “Nikolai Volkoff was so special to my dad and the entire Hart family. We will miss you, Nikolai. My thoughts and condolences go out to Nikolai’s family.”

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Volkoff had his first match in 1968 against Bruno Sammartino. In the ’70s, Volkoff began his WWE (then WWF) tenure as part of tag team The Mongols, which was managed by Captain Lou Albano. They, too, captured the tag titles.

A little later, after a singles run, Volkoff donned a mask and wrestled as a member of Executioners, alongside Big John Studd and Killer Kowalski. This was all before his time with the Sheik.

Alongside the Iron Sheik, Volkoff introduced his trademark promo, insisting the audience rise to their feet while he sang a (purposefully) terrible version of the Soviet National Anthem. Volkoff and the Iron Sheik went on to defeat the U.S. Express, Barry Windham and his real-life brother-in-law Mike Rotundo (father of current WWE Superstars Bo Dallas and Bray Wyatt), for the World Tag Team Championship at the first-ever WrestleMania.

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According to IMDb, Volkoff was filming the currently-in production flick “WrestleMassacre,” at the time of his death. His other on-screen credits include the 2017 animated film “Cool as Hell 2,” “WWF Championship Wrestling” (1972), “WWF All-Star Wrestling” (1972) and “Spectrum Wrestling” (1977).

The cause of Volkoff’s death was not known at the time of publication, and WWE did not immediately respond to TheWrap‘s request for further comment.

See the tweets about Volkoff’s passing below.

MY BEST FRIEND. MY PARTNER. MY BROTHER. WE GET MORE HEAT THAN ANYONE ON EARTH. I TRUST HIM WITH MY LIFE. HE TAKE CARE OF ME WHEN I WAS DOWN. I MISS YOU FOREVER ???? pic.twitter.com/pp7ZgQRDnb — The Iron Sheik (@the_ironsheik) July 29, 2018

I did many road trips with Nikolai Volkoff. As we only lived 15 minutes from each other. I learned so much from him. He was one of the kindest people I’ve ever met. I’ll miss him dearly #RIPNikolaiVolkoff pic.twitter.com/lJG2h01Lto — James Ellsworth (@realellsworth) July 29, 2018

Sad to hear the passing of @WWE Hall of Famer Nikolai Volkoff

Celebrate his life

Watch his greatness on @WWENetwork and all please rise as he sings the Russian National Anthem pic.twitter.com/0m5US6D0tw — Tommy Dreamer (@THETOMMYDREAMER) July 29, 2018

I always loved our conversations backstage … Nikolai Volkoff was so special to my dad and the entire Hart family. We will miss you, Nikolai. My thoughts and condolences go out to Nikolai’s family. ???? pic.twitter.com/WfMd4FDowb — Nattie (@NatbyNature) July 29, 2018