Turkish officials said the killer had been a police officer who, after shooting, shouted: “Don’t forget Aleppo! Don’t forget Syria!” Russia’s Foreign Ministry called the assassination a terrorist attack.
Here’s what we know about Mr. Karlov.
What was his background?
• Mr. Karlov had been Russia’s ambassador to Turkey since July 2013, according to a biography on the website of the Russian Embassy.
• Born in Moscow in 1954, he started his diplomatic career in his early 20s after graduating from the Moscow State Institute of International Relations and the country’s diplomatic academy.
• Mr. Karlov previously served as the ambassador to North Korea. He was married and had a son. According to Russian news agencies, his wife fainted and was hospitalized after being informed of his death.
• Richard Moore, the British ambassador to Turkey, described Mr. Karlov in a tweet after the attack as soft-spoken, hospitable and professional.
His role in Turkey
Mr. Karlov was repeatedly called upon to ease tensions over Russia’s role in the Syrian civil war, which has left hundreds of thousands dead and spurred a refugee crisis that has shaken Europe. After months of fierce bombardment and failed diplomacy, the Syrian government began removing residents from the last rebel-held districts in the city of Aleppo last week.
• After a Russian bombing in northern Syria targeted Turkmen, who were part of the forces against President Bashar al-Assad, Mr. Karlov was summoned to Ankara and asked to convey a firm message to Moscow.
“It was stressed that the Russian side’s actions were not a fight against terror, but they bombed civilian Turkmen villages, and this could lead to serious consequences,” the Turkish Foreign Ministry said at the time.
Tensions escalated, culminating in the Kremlin’s cutting economic ties with Turkey.
How unusual was the assassination?
Historians said the assassination might have been the first of a Russian ambassador since Pyotr Voykov, a Soviet envoy to Poland, was shot to death in Warsaw in 1927.
In the 19th century, Aleksandr Griboyedov, a poet and diplomat, died in Tehran after a mob stormed the Russian Embassy.
What’s the state of relations between Turkey and Russia?
Tensions between Russia and Turkey had been easing recently, and some analysts said that the assassination might bring the countries closer as they sought to take on terrorism.
Televised comments by President Vladimir V. Putin of Russia after the attack seemed to support that view. He said declared that the shooting had been a provocation meant to disrupt the nations’ ties.
Mr. Putin added that there was only one possible reaction: Intensifying the “crackdown on terror.”
The two countries suffered a crisis in their relations last fall. In a paper released in June, Asli Aydintasbas, an international affairs expert at the European Council on Foreign Relations, traced the fault lines to the conflict in Syria.
“Tensions first began to rise as the one-time friends were sucked into the regional struggle for Syria — while Russia backed Assad, Turkey agitated for regime change,” she wrote. “As the alliance unraveled, Moscow broke the silent pact that neither side would support the other’s separatists, and made moves to befriend the Kurds.
But by June, economic actions that Russia had taken against Turkey after the jet was shot down were beginning to pay off as an absence of Russian visitors took a toll on Turkey’s tourism industry.
That month, President Recep Tayyip Erdogan apologized for the downing, writing a letter that said he “would like to inform the family of the deceased Russian pilot that I share their pain and to offer my condolences to them.”
Turkey also announced that it would prosecute a man accused of killing the pilot after his plane was shot downed.
At the time, experts said that Mr. Erdogan’s change of heart on Russia had more to do with the necessities of domestic politics than any kind of broader vision about Turkey’s place in the world.