A Tarrant County medical examiner has ruled that detainee Mack Greer died of natural causes from complications of moyamoya disease, a rare disorder that restricts blood flow to the brain.

Greer, 46, died in June after he was found unresponsive in his cell at the Tarrant County Jail. The medical examiner listed the cause of death as complications of moyamoya disease. Greer was pronounced dead June 18 at John Peter Smith Hospital.

Earlier reporting on the case said Greer had suffered bleeding in his brain. A custodial death report said jail staff found him unresponsive on June 16 while changing bedding in his cell, and he was taken to a medical clinic before being transported for additional treatment.

Greer’s mother, Lea Hurd, disputes the ruling. She said she does not believe moyamoya disease caused her son’s death and said she was not notified by the medical examiner or the sheriff’s office about the official cause and manner of death.