Turkish Interior Minister Suleyman Soylu told journalists that the gunman was identified as Mevlut Mert Altintas, a former special task police officer born in 1994.
Russian Federation and Iran have backed Syrian President Bashar Assad, while Turkey has supported Assad's foes in the four-year long conflict. He was appointed as Russia's ambassador to Turkey in July 2013.
Turkish President Tayyip Erdogan spoke by phone with Russian President Vladimir Putin to share information about the shooting.
The attack comes a day before a meeting of Russian, Turkish and Iranian foreign and defense ministers in Moscow to discuss the future of Syria.
The attack reportedly took place at an art exhibition where Ambassador Andrey Karlov was also present.
Russian Federation has deemed the assassination a terrorist attack while John Kirby, a U.S. State Department spokesman, condemned the assassination as an "act of violence, whatever its source".
The Russian Ambassador to Turkey Andrei Karlov speaks a gallery in Ankara, where he was shot.
He then switches to Turkish, shouting: "Don't forget about Syria, don't forget about Aleppo".
The assassination of Russia's ambassador to Turkey won't derail the improvement in relations between the two countries since a crisis over the war in Syria a year ago, according to politicians and analysts in Moscow. "Terrorism won't sustain. We'll fight it", she said. They should push ahead on all the issues on their agenda and ensure stable relations between Russian Federation and Turkey in memory of Karlov, Slutsky said.
U.S. State Department spokesman John Kirby said U.S. officials were aware of reports about the shooting.
Leonid Slutsky, chairman of the State Duma, said the talks would go ahead despite the killing of the ambassador. Claims and counterclaims from both sides have further complicated ceasefire efforts aimed at providing key humanitarian aid as well as providing a pathway for Aleppo residents to seek refuge in neighboring Turkey. Turkey is a North Atlantic Treaty Organisation ally and part of the US-led fight against ISIS in Iraq and Syria.