An investigation revealed that members of the Gülenist Terror Group (FETÖ) deleted the personal messages of a Turkish police officer, who assassinated Russian Ambassador Andrei Karlov, from his social media accounts and email.The Hürriyet daily reported that during the investigation of Mevlüt Mert Altıntaş, the off duty police officer who killed Karlov, which was carried out by the Ankara Public Prosecutor's Office, it was discovered that the content of Altıntaş's messages on Gmail and Facebook were deleted by FETÖ members connected to his computer from a remote port.

The IP address that was used in the operation was reportedly taken from a U.S.-based company named Express VPN.

It was revealed that the company does not keep log records. In addition, a positive response was not received from the company on IP numbers, as the company was notified that it was not subject to U.S. and European legal rules.

Experts from the Directorate of Cybercrimes reached Altıntaş's iCloud account upon the request of the public prosecutor's office and requested the security code of his mobile phone from Apple to identify the owner of the computer who deleted Altıntaş's messages. However, it was revealed that such a computer did not exist, and the serial number was created on the Internet. The prosecutor's office was also unable to obtain results from the FBI to recover the content of the deleted messages.

Karlov was speaking at the opening of a Russian-themed exhibition in an Ankara art gallery when he was shot dead by Altıntaş. Altıntaş was subsequently killed in a shootout with police inside the gallery. The assassination was at a time of thaw during strained Turkish-Russian relations, and the investigation found that Altıntaş was linked to FETÖ, blamed for last year's coup attempt in Turkey. Since the murder, Ankara and Moscow gradually made progress to rebuild ties that were derailed by the 2015 downing of a Russian fighter jet over the Syrian border by the Turkish military.

Investigators learned that Altıntaş changed his cellphone number a month before the murder and borrowed a new suit from his roommate, Sercan B., who is also a police officer, for "a meeting with a beloved brother," according to the roommate, who was also placed under arrest for his links to Altıntaş. Prosecutors believe the person he met inside a five-star hotel ordered the assassination.Meanwhile, a delegation of Russian officials is visiting Ankara today to investigate Karlov's murder on the anniversary of the assassination.

The delegation consists of a prosecutor, a security attaché and forensic experts who will meet with officials from the Turkish National Police and the prosecutor's office that is conducting the investigation into 2016 killing of Karlov.

The visit comes amid new arrests in the case. A police officer accused of "handling" Altıntaş on behalf of FETÖ was remanded in custody last week, while authorities re-arrested Timur Özkan, the organizer of the exhibition Karlov was attending when he was gunned down in Ankara. Özkan was released earlier but the Sabah newspaper says new evidence showing his connection to Hayreddin Aydınbaş, another FETÖ-linked suspect tied to the murder, was revealed.