Cairo — Mariam Ashraf was an eight-year-old Coptic girl. On Oct. 20, she went with her family to the Church of the Virgin, in Cairo, for a relative’s wedding. She was thrilled with her new hairstyle and the new white dress her mother had bought for the occasion. She stood on the street outside the church with other guests waiting for the bride and groom to arrive. Then a motorbike sped by. On it were two men who opened fire indiscriminately, killing Mariam and three others, and wounding scores of guests. According to an official medical report, eight bullets pierced her body; she died from gunshot wounds to the chest.

Although the Muslim Brotherhood issued a statement condemning the killing, it was just one in a string of attacks carried out on Coptic Christians by Egyptians associated with the Islamist organization.

According to officials in the Coptic Church, there have been attacks on 73 churches, in addition to scores of Coptic-owned homes and businesses, since the end of June. The Copts have been persecuted for joining the demonstrations that led to the removal of President Mohamed Morsi in early July. Supporters of Mr. Morsi were incensed that the Coptic pope, Tawadros II, supported the army’s plan for ending the Brotherhood’s rule.

It is not only the Copts who have suffered from political violence since the summer. Ongoing attacks by Morsi supporters against soldiers and police officers have caused hundreds of deaths. Egyptian television broadcast a report showing Islamists attacking a police station in the town of Kerdasa on Aug. 14 with rocket-propelled grenades, causing the deaths of 15 policemen. They stripped the bodies and paraded them on the street.