By Ferdi Uzun

AYDIN, Turkey (AA): Six people, who were arrested in the aftermath of the murder of the Russia’s envoy to Turkey, were released on Thursday, police sources said.

Altintas’s parents, sister, two uncles and aunt were released early in the morning in Turkey’s Aegean province of Aydin, said the sources who spoke on condition of anonymity due to restrictions speaking with the media.

Ambassador Andrey Karlov died on Monday after being shot multiple times at an art exhibition in Ankara. He was delivering a speech when the assailant, 22-year-old off-duty policeman Mevlut Mert Altintas, opened fire.

In total, 13 people were arrested including Altintas’s roommate in Ankara.

Kremlin spokesman Dmitry Peskov said Wednesday the assassination of Russia’s envoy to Turkey was a “stab in the back” for Turkey.

“Turkish side did not want this incident to happen. That is why, this attack was a stab in the back for Turkey too,” Peskov said in an interview with the Mir TV Channel.

Andrey Karlov died on Monday after being shot multiple times at an art exhibition in Ankara. He was delivering a speech when the assailant, 22-year-old policeman Mevlut Mert Altintas, opened fire.

Peskov said the timing of the incident was not a “coincidence”, adding: “This was a unique case in the history of Turkish-Russian relations.”

He added President Vladimir Putin condemned the attack and called it as a terror act, which aimed at normalization process between the two countries.

Peskov said the assassination was “emotionally very difficult” news for Putin.

Meanwhile, Duma, the lower house of Russia’s parliament, issued Wednesday a statement condemning the assassination of Karlov and calling for counter-terrorism cooperation.

A funeral service for Karlov will be held at noon on Thursday in the Cathedral of Christ the Savior. Putin postponed his annual news conference to attend the ceremony.

Putin signed an executive order awarding Karlov the title of the Hero of the Russian Federation, Kremlin said in Wednesday’s statement.

An investigative team from Russia met anti-terrorism police in Ankara on Wednesday as part of a joint probe into Monday’s assassination of Ambassador Andrey Karlov, according to a police source.

The Russian team comprises 18 officials, including a prosecutor and two defense attaches. They arrived in Ankara on Tuesday afternoon.

The two countries agreed to establish a joint commission to investigate the murder, a police source, who spoke on condition of anonymity, said.

A total of 120 people in the Ankara Police Department, including anti-terrorist unit personnel and interpreters, have been assigned to work and cooperate with the Russian team.

An investigation team from Ankara Public Prosecutor’s office has examined footage of the incident and listened to eyewitness statements.

Investigators also inspected the suspect’s phone conversations and searched whether he had any connection with Russian embassy staff in Ankara.

According to initial reports, the assassin had links to the Fetullah Terrorist Organization (FETO), which the Turkish government accuses of staging the deadly July 15 coup attempt.

Investigators found that the gunman, 22-year-old police officer Melvut Mert Altintas, was on a three-day vacation during the failed coup and passed the period in Ankara. Now they are investigating what he was doing in the Turkish capital at that time.

Altintas also took a day’s sick leave this Monday, producing a medical report. Before the assassination, Altintas spent two hours in a hotel where he had reserved a room previously.

His name had been found in a witness list for a FETO probe in Istanbul and one of his uncles was the head of a coaching center which was later closed for links to the terror network. Some of Altintas’s colleagues had also been dismissed for being FETO members.

Prosecutors are also investigating why the attacker could not be taken alive. Initial findings suggest he continued firing at police officers, shouting: “You cannot capture me alive.” Officers shot Altintas in the legs but he continued to shoot while crawling on the ground.

According to information compiled from footage and witnesses, police neutralized the attacker around 40 minutes after he shot the Russian envoy.

The joint team is expected to work for at least a week in the Turkish capital.

* Diyar Guldogan in Ankara contributed to this report

[Photo: Turkish Foreign Minister Mevlut Cavusoglu offers condolences to Marina Karlov (C), widow of deceased Russian ambassador to Turkey Andrei Karlov after the coffin of Andrei Karlov arrived at Vnukovo International Airport in Moscow, Russia on December 20, 2016. Photgrapher: Muhabiri Foreign Ministry/AA]