Another dead Russian diplomat

Nine Russian diplomats have died over the past year. Authorities claim that the death of Russian ambassador to Sudan, Mirgayas M. Shirinskiy, "appeared to have symptoms consistent with a serious heart seizure". However, a number of the other recent deaths of Russian diplomats have been described in the same terms despite evidence to the contrary. Diplomat Vitaly Churkin died on February 20th after suddenly becoming ill on his way to work, the death was initially attributed to a heart attack, but doctors later said the death required further study. In another report from November 8th 2016, first reported that Russian diplomat Sergei Krivov died after falling from a roof, Russian officials then flipped their story to say Krivov died from a heart attack instead. Why are so many Russian diplomats dying?