Turkey and Russia have launched a joint investigation into the assassination of Russia's ambassador to Turkey at the opening of a photo exhibit in the capital, Ankara, on Monday.The ambassador, Andrei Karlov, was gunned down as he gave a speech at an art gallery. Turkey has identified the attacker as Mevlut Mert Altintas, a 22-year-old riot police officer, who shouted to the crowd, "Don't forget Aleppo! Don't forget Syria!" He was killed by Turkish special forces at the scene.A 18-member Russian investigations team has arrived in Ankara and has examined the crime scene and well as the bodies of the ambassador and the gunman, Turkey's state-run Anadolu news agency reported. Police arrested "six relatives and a roommate of the assassin," but later released his uncle "under judicial restrictions.""The envoy's autopsy has been completed and his remains have been sent to Ankara's Esenboga International Airport for a state ceremony before repatriation to Russia," Anadolu said.Meanwhile, a few more details are emerging about Altintas. This is what a "senior security official" told Reuters: "On Monday morning, Altintas called the division of the Ankara riot police where he had worked for 2-1/2 years and said he was unwell and would bring a doctor's note upon his return, the official said. "Altintas, who lived in a shared flat in the Demetevler neighbourhood on the outskirts of Ankara, spent the night before the attack at a hotel in central Ankara close to the gallery, the official said."Additionally, a senior government official told The Associated Press that Altintas "was unlikely to have acted alone."Turkish Foreign Minister Mevlut Cavusoglu said the street where Russia's embassy lies will be renamed Karlov Street to honor the assassinated diplomat, Anadolu added.Turkish President Recep Tayyip Erdogan called the killing a provocation against warming relations between the two countries, Anadolu reported, and said Turkey would not "let terror hitch us to its own agenda."Additionally, "hours after the shooting, shots were fired at the American Embassy, which is closed for business along with U.S. Consulates in Istanbul and Adana," NPR's Peter Kenyon reported from Istanbul. "Iranian diplomatic missions are also closed."Russia is a close ally of the regime in Turkey's neighbor, Syria, and is waging an airstrikes campaign there.Today, Russia is hosting talks with the foreign ministers of Turkey and Iran on the war in Syria. Copyright 2016 NPR. To see more, visit http://www.npr.org/.