Russia has a long history of Heads of State/Govt dying from unnatural causes, here from 1547:
Feodor II (1589-1605, ruled 1605) Strangled
False Dmitry I (1582-1606, ruled 1605-1606) Killed
Vasili IV (ca. 1552-1612, ruled 1606-1610) Killed Died in custody
Ivan VI (1740-1764, ruled 1740-1741) Killed by his guards in custody
Peter III (1728-1762, ruled 1762) Stroke/Assasinated
Paul I (1754-1801, ruled 1796-1801) Assasination/coup: hit with a box, strangled
Alexander II (1818-1881, ruled 1855-1881) Assasinated with a bomb
Pyotr Stolypin (1862-1911, Head of Govt 1906-1911) Assasinated
Boris Shtyurmer (1848-1917, Head of Govt 1916) Killed Died in custody
Ivan Goremykin (1839-1917, Head of Govt 1906) Killed in a robbery
Nicholas II (1868-1918, ruled 1894-1917) Executed
Viktor Pepelyayev (1885-1920, Head of Govt 1919-1920) Executed
Nikolai Golitsyn (1850-1925, PM 1917) Executed
Lev Kamenev (1883-1936, "Head of State" 1917) Executed
Ivan Syrtsov (1883-1937, Head of Govt 1929-1930) Executed
Daniil Sulimov (1890-1937, Head of Govt 1930-1937) Executed
Alexei Rykov (1881-1938, Premier 1924-1930, Head of Govt 1924-1929) Executed
Mikhail Rodionov (1907-1950, Head of Govt 1946-1949) Executed
Yegor Gaidar (1956-2009, Acting PM 1992) Complications from poisoning Pulmonary edema
Vladimir Putin (1952-Unfortunately not yet, hopefully soon...