Özgür Dengiz was born in 1984 in Ankara, Turkey, to a father who was a veteran of the Turkish invasion of Cyprus and a mother who worked as a seamstress. He frequently clashed with his parents and often ran away from home. After completing middle school, he did not pursue further education. At the age of 17, Dengiz killed a friend during an argument and was sentenced to 10 years in prison, serving only three years before being pardoned by President Ahmet Necdet Sezer. 

Following his release, he enlisted in the army but faced multiple hospitalizations due to psychological issues and attempted to desert several times. After his military service, his mother opened a tailor shop for him, but he showed little interest in managing it.

In 2007, Dengiz embarked on a series of violent crimes:​

June 5, 2007: He killed Sedat Erzurumlu, a computer engineer, after becoming enraged when Erzurumlu suggested he couldn't afford a laptop he was interested in. Dengiz stole two laptops and Erzurumlu's mobile phone.

September 12, 2007: Dengiz shot and killed a garbage collector at the Mamak Dump. 

September 12, 2007 (later that day): He encountered Cafer Er, a 55-year-old municipal worker, and after a brief conversation, shot him twice in the head from behind. Dengiz then skinned Er's body with a cleaver, consumed some of the flesh raw, stored portions in his bag, and placed the wrapped body in his car trunk. He later disposed of the corpse at the Mamak Dump and returned home, where he stored remaining flesh in the refrigerator and fed some to stray dogs. 

Authorities discovered Er's mutilated body at the Mamak Dump, with significant flesh missing. Investigations revealed that Er was last seen arguing with a young man in a park. Police traced Dengiz using call records from the stolen mobile phone of his earlier victim, Erzurumlu, which Dengiz had lost at the crime scene. A search of Dengiz's apartment uncovered fresh human flesh in the refrigerator, later identified as parts of Er's body. 

Dengiz exhibited no remorse during questioning, expressing an irresistible urge to consume human flesh and laughing intermittently. He stated he would have continued killing if not apprehended. Initially sentenced to two life terms, Dengiz's conviction was later overturned due to a ruling by the Court of Cassation of Turkey, which deemed him insane and unfit to stand trial. Consequently, he was committed to a psychiatric facility.