An Iranian man arrested last year during nationwide protests over the death of a 22-year-old woman detained over her headscarf has died after suffering a convulsion in prison, state media reported Thursday.

Javad Rouhi, 35, suddenly fell ill while awaiting resentencing after Iran's Supreme Court overturned his death sentence, according to the state-run IRNA news agency. He was taken to a local hospital in the city of Noshahr on the Caspian Sea, some 60 miles north of the Iranian capital, Tehran, and pronounced dead there.

Authorities were investigating his death, IRNA said.

Iranian authorities had accused Rouhi of burning a Quran, an act that carries a death penalty, during protests in Noshahr over the death of Mahsa Amini, However, Amnesty International said authorities detained Rouhi over an online video that showed him dancing at a demonstration.

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Amnesty said members of Iran's paramilitary Revolutionary Guard severely beat and flogged Rouhi, shocked him with stun guns, exposed him to freezing temperatures and put guns to his head to force him into confessing.

The protests began in September 2022 when Amini died after being arrested by Iran’s morality police for allegedly violating the Islamic Republic’s strict dress code requiring women to wear the hijab, or Islamic headscarf.

More than 500 people were killed and 22,000 others arrested in a security crackdown on the demonstrations. The protests marked one of the biggest challenges to Iran’s theocracy since the 1979 Islamic Revolution.

With the one-year anniversary of Amini's Sept. 16 death approaching, authorities already are detaining activists and others.