Photographer Burhan Ozbilici was attending an exhibition in Ankara when Mevlut Mert Altıntas shot and killed Andrei Karlov.
Here Ozbilici, who works for the Associated Press, describes what happened:
The event seemed routine, the opening of an exhibit of photographs of Russia. So when a man in a dark suit and tie pulled out a gun, I was stunned and thought it was a theatrical flourish.
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. Full Article here: :https://www.theguardian.com/world/2016/dec/20/photographer-burhan-ozbilici-killing-turkey-russian-ambassador-andrei-karlov