A man lays a bunch of flowers to express condolence of Russian Ambassador to Turkey Andrey Karlov who was killed in a gunman attack, in front of the Russian Foreign Ministry in Moscow, Russia, Dec. 20, 2016. The Russian Ambassador to Turkey Andrey Karlov was killed in a gunman attack at an art exhibition on Monday in the Turkish capital of Ankara, according to the Russian Foreign Ministry. (Xinhua/Evgeny Sinitsyn)