The former vice president of Iran and mayor of Tehran, as well as a confidant of President Hassan Rouhani, turned himself into authorities Tuesday, telling them that he killed one of his two wives.

Mohammad Ali Najafi allegedly murdered Mitra Najafi seven hours before walking into the police station, Iranian news outlet Radio Farda reported. The outlet reported that he appeared calm after confessing, and was filmed shaking hands with the police chief.

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Prosecutor Mohammad Shahriari was quoted by the Iranian Students’ News Agency, or ISNA, as saying that the former official, who is 68, told police he and the victim, 35, had been having marital problems.

Mohammad Ali Najafi

Najafi resigned as mayor in 2018 after hard-liners criticized him for attending a dance performance by young girls. He had also been criticized for marrying his much younger second wife, with the controversy helping doom his political career. Polygamy is legal in Iran.

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Najafi told police in his confession that Mitra had constantly threatened to reveal his secrets -- which were not described -- and ruin him, Radio Farda reported.

Gun violence is very rare in Iran, especially among the country's political and economic elite.

Gen. Ali Reza Lotfi, head of Tehran police's criminal investigation department, told state TV that Najafi handed the weapon over to police voluntarily and admitted committing the crime.

Lotfi said Najafi fired five times, hitting the victim twice. He said the case is under investigation by the police and judiciary simultaneously.

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Mitra's body was found in a bedroom on the 7th floor of a residential high-rise in northern Tehran, according to the semi-official news agency Tasnim.

The Associated Press contributed to this report.