Hundreds of Christians gathered at a Coptic mass at Saint Mark's Coptic Orthodox Cathedral in Cairo on Tuesday evening. Families of the victims also gathered in the church. Of the 21 men executed by Islamic State, all were Christian. The Copts were taken hostage by the Islamic State last month while residing in Surt, Libya. sign up to our newsletterIn the video produced by Islamic State media, “A Message Signed with Blood to the Nation of the Cross,” the Copts were beheaded by the militants. In the video, militants suggested that these killings were in response to both the death of Osama bin Laden as well as a five-year-old dispute over the disappearance of a Coptic Christian woman.The Egyptian government knew of the disappearance of the victims 45 days before their death, but refrained from taking action to rescue them, according to a statement from the Mapsero Youth Movement. Furthermore, they claim that even though the families of the victims repeatedly begged the government to intervene, they choose silence over action. On Sunday, Egyptian President Abdel Fatah el-Sisi announced seven days of national mourning in reaction to the killings. In a televised address he said that Egypt would take necessary action to avenge the deaths. On Monday morning Egypt announced that it had carried out airstrikes against Islamic State targets in Libya. Egyptian Prime Minister Ibrahim Mehleb announced in an official statement that the families of the victims will be granted "martyr privileges," including pensions from the Ministry of Social Solidarity as well as a new church to be built in Al-Minya, in honor of the victims.