Istanbul Church Attack - Gunmen kill one person during Sunday morning mass
In a Telegram statement, the gang claimed that two of its militants carried out the attack before fleeing to safety.
CCTV footage obtained by Turkish media depicts the moment of the incident. Worshippers were on their feet, facing the altar, when two shooters entered the church from the back.
They looked to be pursuing a man who had just entered. After he was shot and killed, the shooters departed peacefully.
The 19th-century church is located behind high walls on the Bosphorus on Istanbul's european side, near a tiny fish market. The streets surrounding it have been cut off by police.
Inside the church, detectives obtained statements from individuals present when the assailants struck.
The Turkish Interior minister, ali Yerlikaya, who visited the scene, stated that a man known only as CT perished in the incident.
Speaking to reporters outside the church, Istanbul governor Davut Gul stated that the victim was a Turkish national and that no one else was harmed. He said the assailants only shot at one person.
The motivation for the attack and why the victim was targeted were not immediately known.