A senior leader of the outlawed Muslim Brotherhood died of a heart attack on Thursday in a Cairo, Egypt prison where he was serving 25-year multiple sentences including on terror-related charges, his lawyer said.

The lawyer, Abdel Moneim Abdel Maqsoud, said Essam el-Erian, 66, was arrested in 2013, following the military overthrow of Egypt’s first democratically elected president, Mohamed Morsi, who hailed from the Brotherhood’s ranks.

“The authorities notified me of his death, and I informed his family to arrange for receiving his body (for burial),” lawyer Abdelmoneim Abdelmaqsood told AFP.

Since Morsi’s overthrow, the authorities designated the Muslim Brotherhood as a terrorist group, imprisoned thousands of its members and cracked down heavily on dissent.

El-Erian isn’t the first Muslim Brotherhood leader to die behind bars. A year ago, ousted President Morsi collapsed in court while standing trial. The UN rights experts said then that Morsi was denied medical care, suffered recurrent diabetic comas and lost vision in one eye, concluding that the conditions he endured ‘could add up to a state-sanctioned arbitrary killing’.

Morsi died in custody in June 2019, after falling ill during a court hearing. Same as other Muslim Brotherhood leaders, el-Erian stood several trials and faced a plethora of terror-related charges.

A Cairo court set the senior leader’s execution in 2018, with ten members of the Muslim Brotherhood. They were convicted of setting up an armed sit-in, vandalizing public property, and additional counts on the killing of policemen and an Egyptian citizen. El-Erian’s lawyer had appealed the verdict.