Mevlut Mert Altintas
Who is he?
A Turkish police officer who was standing behind Russia's ambassador to Turkey, Andrei Karlov, as he gave a speech at an art gallery in the Turkish capital.
Moment later, he drew a handgun and shot Karlov nine times before reportedly shouting "Allahu Akbar."
He is understood to have added, in a mixture of Turkish Arabic, words to the effect of: "We made an oath to die in martyrdom...it is revenge for Syria and Aleppo...until they are safe, you will not taste safety."
Russia's foreign ministry has described his actions as a "terrorist attack."
What do we know about him?
Melih Gokcek, the mayor of Ankara, has confirmed that the gunman worked in the city as a police officer, but little else is known about him at this early stage.
Turkish media reports say he was 22 years old, and one local newspaper described him as an "agile" police officer who worked on special operations.
A pro-government newspaper, Yeni Şafak, said he had worked for Ankara's riot police.
He was clean-shaven and wore a black suit with a matching belt and tie.
Seconds before the attack he was captured on camera by an AP photographer standing innocuously behind Karlov as he gave a speech.
According to CNN, the words spoken by the attacker are similar to the unofficial anthem of the Al Qaeda-allied group Al Nusra.
A picture of the gunman wearing his police uniform has been widely circulated by the Turkish media, which identifies him as M. Mert Altintas.
Police officers standing outside the gallery said they believed the gunman was off-duty when the attack took place.
Turkish media reports said the gunman attended Korfez Preparatory School.
Who is he?
Born in Moscow in 1954, Karlov Andrei Gennadyevich was educated at the Moscow State Institute of International Relations and the Diplomatic Academy.
He began his career with the government at the Ministry of Foreign Affairs of the USSR in 1976.
He went on to hold various diplomatic positions at the Russian embassy to North Korea.
Karlov has been Russian ambassador to Turkey since July 2013.
Why is the attack on Andrei Karlov important?
The attack on Andrei Karlov came after days of protests in Turkey over Russia's role in Syria, although Moscow and Ankara are now working closely together to evacuate citizens from Aleppo.
The attack happened at the Cagdas Sanatlar Merkezi, a major art exhibition hall in the Cankaya district of Ankara where most foreign embassies are located including Russia's mission.
Protesters in Turkey have held Russia responsible for human rights violations in Aleppo.