Andrei Karlov, the Russian ambassador to Turkey, was shot and killed today by 22-year old Mevlüt Mert Altintason on live camera.
The assassin yelled Allahu Akbar" and then screamed in Turkish "We die in Aleppo, you die here," a reference to the atrocities going on in Syria's largest city.
The killing comes after a week of protests in Turkey over Russian involvement in the Syrian conflict.
Altintas, an off-duty police offier, was shot dead after a 15 minute standoff with special forces. Three others were injured in the incident.
Given the United States's tricky relationship with both Turkey and Russia, this development will be a huge challenge for the current President Barack Obama and the President Elect Donald Trump.
So far neither has commented.