It’s been a week since the news broke of Russia’s most popular dissident Alexei Navalny’s death. But what caused his death, still remains a mystery. Many are alleging that Vladimir Putin's most vocal critic was most likely killed with a punch to the heart. It's a technique often used by KBG operatives, after being exposed to sub-zero temperatures for several hours. Russian authorities claim Navalny collapsed after a walk in an Arctic penal prison, where he had been serving a 19-year sentence. Navalny's family was told that he died of 'sudden death syndrome' but his body has still not been handed over.