Authorities believe Şahin Söğüt, a suspected member of the Gülenist Terror Group (FETÖ) implicated in the murder of Russian Ambassador Andrei Karlov, was ordered to remain silent by the terrorist group. Söğüt is currently being jailed for the 2016 assassination of Karlov committed by off-duty police officer Mevlüt Mert Altıntaş. Altıntaş was killed in a shootout with police, and Söğüt was arrested on suspicion of acting as a handler for Altıntaş on behalf of FETÖ.

Demirören News Agency (DHA) reported yesterday that the terrorist group sent a message to Söğüt to tell him not to speak to authorities about the case. DHA says Söğüt, a key figure in the assassination, decided to speak out about his connection to the terrorist group and told prosecutors in his initial interrogation that he would "decide what to do next." When his lawyer Sabiha Nur Gümüş conveyed his remarks to the senior cadres of FETÖ, the terrorist group sent him a message through Gümüş.

Gümüş was under surveillance by authorities expecting her to carry correspondence between suspects and FETÖ members and during an interview with her client in April 2018, she secretly showed a note to Söğüt, allegedly instructing him to keep his mouth shut and giving him assurance that his family will be cared for while he is in prison. Gümüş, later detained on suspicion of membership in FETÖ, denied sending the note to Söğüt and claimed it was "a misunderstanding." She was later released under judiciary control, but prosecutors sought her arrest. An investigation found out she was smuggled out of the country by FETÖ members and remains at large. Söğüt, meanwhile, continues exercising his right to remain silent.

Prosecutors say FETÖ and "foreign powers that used the group" had aimed to derail Turkey-Russia bilateral relations through the assassination and "drive the countries toward a possible conflict" as well as "create chaos ahead of the July 15, 2016 coup attempt" by FETÖ.