Iran’s judiciary confirmed the death of Shahin Naseri in its custody. Naseri was known for his horrifying account of torture against executed wrestler and political prisoner Navid Afkari.

On Thursday, two days after Naseri’s death was reported by activists, the head of Iran’s Prisons Organization issued a “special directive” for a probe into the case. In a separate statement circulated on Iranian media, authorities at Tehran’s Greater Prison announced that Naseri had died “45 minutes” after being transferred to the jail’s medical center. With no further details on the exact circumstances surrounding the victim’s death, the statement said a full explanation was pending the completion of forensic examinations.

However, according to accounts by other inmates at the same jail, the day before his death Naseri had been summoned by intelligence interrogators and taken to solitary confinement. “He was neither suicidal nor suffering from any medical condition,” the prisoners were quoted as saying by the Oslo-based Iran Human Rights Organization.

The center also reported that Naseri had intended to release a new statement on the anniversary of Afkari’s execution over the phone from inside the prison before his plan was detected by the guards.