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He gunned down Andrei Karlov, 62, as the ambassador gave a speech in Ankara. The attack was filmed and shared widely on social media, and the shooter was heard shouting, "Don't forget Syria and Aleppo!" He was later shot and killed by security forces. Russia is an ally of Syrian President Bashar al-Assad, and has intervened militarily in the country's civil war; Turkey has backed some groups of opposition forces.
In a televised statement, Turkish President Recep Tayyip Erdogan called the murder a "provocation" meant to harm the country's ties with Russia. Russian President Vladimir Putin said the only response to the assassination is "stepping up the fight against terrorism."