Turkish policeman Mevlüt Mert Altıntaş, who fatally shot Russian Ambassador to Turkey, most likely didn’t act alone, Associated Press reports, citing a source in the Turkish Government.

The agency interlocutor described the killing as “fully professional, not a one-man action.”  In his words, the attack was well-planned, RIA Novosti reports.  

On Monday evening, a gunman attacked Russian envoy to Turkey, Andrei Karlov, while the latter was giving a speech at a photo exhibition dedicated to Kamchatka at Çağdaş Sanat Merkezi Contemporary Arts Center of Ankara.

The gunman shot the ambassador in the back, following which he uttered words related to Aleppo and Syria as well as shouted “Allahu akbar (God is great).”

Karlov was rushed to hospital in critical condition, but he could not be saved. 

The assailant, who was shot dead by police 45 minutes after the assault, was later identified as Ankara police officer Mevlüt Mert Altıntaş.

Russian Ministry of Foreign Affairs described the incident as a terrorist attack.