When a neatly dressed man fired at the Russian ambassador to Turkey, a veteran photographer covering the "routine" event thought it was a "theatrical flourish".

Instead, Associated Press photographer Burhan Ozbilici's photos captured the assassination of Russian ambassador Andrei Karlov at an art gallery in Ankara as it happened.

In a first-person account for AP, Mr Ozbilici said the gallery event was routine, the opening of a Russian photography exhibition.

"So when a man in a dark suit and tie pulled out a gun, I was stunned and thought it was a theatrical flourish," he said.

"Instead, it was a coolly-calculated assassination, unfolding in front of me and others who scrambled, terrified, for cover as the trim man with short hair gunned down the Russian ambassador."

At least eight shots were fired in the pristine art gallery, causing pandemonium to break out.

"People screamed, hid behind columns and under tables and lay on the floor. I was afraid and confused, but found partial cover behind a wall and did my job: taking photographs."

The photographer had only decided to attend the exhibition, titled "From Kaliningrad to Kamchatka" because it was his way home from the Ankara office.

The speeches had already begun by the time he arrived.

"After Russian Ambassador Andrei Karlov began to make his address, I moved closer to photograph him, thinking the pictures would come in useful for stories on Turkish-Russian relations."

As much as Ozbilici could tell, the ambassador was speaking lovingly about his homeland, appearing calm and humble.

Then came the gunshots in quick succession.

"The ambassador's body lay on the floor, just meters away from me. I couldn't see any blood around him; I think he may have been shot in the back.

"It took me a few seconds to realise what had happened: A man had died in front of me; a life had disappeared before my eyes."

The photographer moved to the side of the room while the gunman, who was later identified as police officer Mevlut Mert Altintas, gestured with his gun at people cowering on the right side of the room.

At first, he thought Altintas might be a Chechen militant. Others said he was shouting about the Syrian city of Aleppo.

"So he was probably angry about Russian bombardments of Aleppo that were aimed at driving out anti-government rebels. Many civilians have been killed in the fighting.

"He also shouted 'Allahu Akbar', but I couldn't understand the rest of what he said in Arabic."

Ozbilici reports the gunman was agitated, even walking around the ambassador's body and  smashing photos hanging on the wall.

"I was, of course, fearful and knew of the danger if the gunman turned toward me. But I advanced a little and photographed the man as he hectored his desperate, captive audience.

"This is what I was thinking: I'm here. Even if I get hit and injured, or killed, I'm a journalist. I have to do my work. I could run away without making any photos. ... But I wouldn't have a proper answer if people later ask me: 'Why didn't you take pictures?'"

- with AP