The Russian ambassador to Ankara was killed in an attack at an art gallery in the Turkish capital on Monday, reported The Guardian. Andrei Karlov was attending an exhibition, “Russia as seen by Turks”, at the venue when an unidentified gunman opened fire in the gallery.

The gunman stood behind Karlov while he was making his speech. He was reportedly killed by the police after the incident. A video from the incident shows Karlov making a speech at the event when the gunman started firing indiscriminately, reported BBC. The gunman is also reported to have been heard saying, “Don’t forget about Aleppo, don’t forget about Syria”, in the video.

The US state department spokesperson John Kirby said they had intelligence reports about a probable attack on Karlov. “We condemn this act of violence, whatever its source,” Kirby said. “Our thoughts and prayers are with him and his family.”

This comes a day after protests in Turkey against Russia’s role in the Syrian war. Russia-backed pro-government forces recently announced that the battle with the rebels was over after they took over east Aleppo, which was the last stronghold of the rebel fighters. Russia has faced strong criticism for alleged human rights violations in the war.