Erich Albert

Erich Albert (died 1914) was a German general during World War I and a member of the Templar Order. During the war, the Germans and British called a truce on Christmas. When Albert became comfortable with the truce, he invited a British medic to the German camp to perform surgery on a German soldier. As soon as the surgery was done, the medic noticed Albert's ring, which had a red cross on it. Albert offered to trade it with him, but when the medic raised his hands to show that he had no ring in return, Albert noticed the Assassin burnmark on the medic's ring finger. The medic immediately impaled Albert with his hidden blade, killing him.

Source

 * Assassin's Creed: Project Legacy - Holidays - Chapter 1 - Ghosts of Christmas Past