Istanbul airport killing 44 people and injuring hundreds more. Investigators identifying the men as citizens of russia, uzbekistan and kyrgyzstan. Officials believe the bombers entered turkey about a month ago from the isis stronghold of raqqah in syria bringing with them the suicide vests and bombs used in the attack. The terrorists rented an apartment in an istanbul neighborhood thats known for its proisis rallies. For the very latest on this, lets go to cnns alexandra field in istanbul. Whats the latest on the investigation . Sources told cnn they believe this attack was closely directed by isis, and now u. S. Officials are telling cnn they believe the ringleader of this attack is a wellknown militant from the north caucus region of russia. Thats the person who they believe gave orders to the three men who had spent time in syria according to sources and who then entered istanbul about a month ago renting an apartment here. That apartment has been at the center of the investigation