If you think the assassination of the Russian Ambassador to Turkey, the same day terrorist attack in Berlin, and the announcement the next day of an agreement by Russia, Turkey, and Iran to end the Syrian civil war are all a monumental coincidence, then you haven't been paying attention.
Aside from the requisite "Allahu Akbar!", Mevlut Mert Altintas, the Russian Ambassador's killer – a police officer – shouted "Don't forget Aleppo! Don't forget Syria!" That's what's being reported widely, but he also said, according to the Daily Mail, in Arabic:
"'We are the descendants of those who supported the Prophet Muhammad for jihad.' According to local media, his words are similar to the unofficial anthem of Al Nusra. Some reports claimed he said words to the effect of: 'We made an oath to die in martyrdom … it is revenge for Syria and Aleppo … until they are safe, you will not taste safety.'"