Karlov, who was appointed as Moscow's man in the capital since July 2013, was married, and had a son, according to the Russian Embassy
He had served as ambassador at a fractious time in Russian-Turkey ties; diplomatic relations hit a low after Turkish forces shot down a Russian fighter jet near the Syria border in November 2015.
In the wake of that attack, Karlov accused Turkey of encouraging an anti-Russia campaign, in an interview with Russia's state-run TASS
"Of late, Turkey more often makes unfounded accusations, in particular, that Russia's military aircraft allegedly violate the airspace," he said. "Most often, this misinformation launches anti-Russian campaigns in the Turkish mass media or becomes their part."
Russian airstrikes in Syria, which borders Turkey, have been conducted to bolster President Bashar al-Assad's regime. Russia has said it's coordinating with the Syrian regime to target ISIS and other terrorists.
'Quietly spoken professional'
Richard Moore, Karlov's British counterpart in Turkey, tweeted of his shock. He described the ambassador a "quietly spoken, hospitable professional."
Sir Tony Brenton, who was Britain's ambassador to Moscow from 2004 to 2008, did not know Karlov. However, he told CNN: "As a former ambassador myself, you always know you're a symbol and also a target. Something like this is particularly horrifying when it happens. My first thought was sympathy for his family and colleagues."
Karlov was born in the capital of the then-Soviet Union in 1954, and began his diplomatic career in his early 20s, after studying at Moscow's State Institute of International Relations.
An English and Korean speaker, he previously served as Russia's ambassador extraordinary to the Democratic People's Republic of Korea (North Korea).