Russian animator Pavel Muntyan said in a post on Facebook:
"I can't believe [it]... I have a lump in my throat. It just can't be! How so?" said Muntyan, a producer at Russian animation studio Toonbox said on Wednesday. "Sergey was one of the most athletic and healthy people I knew! Like a bull!"
According to Muntyan, Karshkov died in a Swiss clinic after a medical examination. The MRI fluid allegedly caused an allergic reaction, after which he fell into a coma and died.
"He went to Switzerland for a checkup... Contrasting fluids for MRI and the subsequent MRI led first to allergies, then to a coma, and then to death," he wrote. "Oh my god what a nightmare!! A NIGHTMARE!"
Karshkov, a founder of the Cyprus-based online bookmaker 1xBet, was born in Ukraine's Kyiv region in 1980 and later moved to Bryansk in Russia, where he headed the department for combating cybercrime in the regional department of Russia's Ministry of Internal Affairs.