The bombing came on a public holiday in Egypt, commemorating the birthday of the Prophet Muhammad. Though that is a Muslim celebration, the church was filled with more than the usual number of congregants taking advantage of the day off.
When the bomb detonated, Farag, 80, was seated on the left side of the church. His wife, Samiha Tawfik, was on the right side, along with the other female congregants.
"I could not see anything," recalled Farag. "We were all in shock, covered in dust, running through corpses that got thrown by the intensity of the blast."
Unable to breathe from the dust, his head pounding, he stumbled around the pews. Soon, he began to see, and understand, what had happened.
"A minute passed by and I started to see flesh scattered everywhere around us," he said. "Even the ceiling had collapsed."
He couldn't find his wife.
Egypt's Orthodox Coptic Christian community, which makes up 10 per cent of the population, has long felt discrimination at the hands of the country's Muslims, as well as successive secular but authoritarian rgeimes.
And attacks on Christians have intensified since the 2011 populist revolt that ousted President Hosni Mubarak. At least 26 sectarian assaults have targeted the community this year alone, according to human rights activists.
But the bombing was the gravest sectarian attack on Christians in recent years. St Peter's Church is located inside the St Mark's Coptic Orthodox Cathedral complex in the heart of Cairo. The cathedral houses the headquarters of the Coptic Orthodox Church in Egypt, as well as the home of its leader, Pope Tawadros II.
Over the past six years, numerous attacks on Christians have left scores dead. On January 1, 2011, the Church of Saints Mark and Peter in the northern city of Alexandria was bombed, killing 23 people as they left the New Year's Day service. Ten months later, Egypt's security forces killed 28 Christians protesting the demolition of a church, claiming the protesters first attacked them.
In 2013, Christians were targeted in a spate of attacks after Egypt's elected Islamist president, Mohammed Morsi, was ousted in a military coup.
President Abdul-fattah al-Sisi, the former general who led the coup, condemned the attack and declared three days of mourning.
"Vicious terrorism is being waged against the country's Copts and Muslims," he was quoted as saying on local television networks. "Egypt will emerge stronger and more united from this situation."
In Washington, the US State Department declared: "The United States condemns in the strongest possible terms the terrorist attack today on Christian worshippers outside St Mark's Cathedral."
In New York, the United Nations Security Council likewise condemned "the heinous and cowardly terrorist attack".
Analysts focusing on Egypt's religious divides said the Government has made previous promises to apprehend the perpetrators of hate crimes. But it has shown few results.
"Sectarian tensions in Egypt is ongoing and this attack, although shocking in its scope, is not an aberration," said Amira Mikhail, a fellow at the Tahir Institute for Middle East Policy. "Despite the shift in public rhetoric by President Sisi in which he has called for religious reform and has visited the cathedral on several occasions, little has been done to actually change the institutionalized sectarianism in the Government and the continued violence perpetrated by non-state actors."
Some reports on local television networks suggested that a bomb was placed inside a handbag in a section of the church designated for female worshippers. A large proportion of the victims were women, according to local reports.
Senior Egyptian officials, including the prime minister and interior minister, arrived at the church shortly after the attack. They were greeted by a small group of angry protesters who railed against the continuous attacks on Christians, as well as the security forces' failure to stop the attacks.
"The police are thugs," some in the crowd chanted.
"The people demand the removal of the regime," others chanted.
Farag and other witnesses said they noticed no police or guards at the entrance to the church, although there's typically a heavy security presence at the cathedral to provide protection for Pope Tawdros II.
At Al-Demerdash Hospital, where most of the victims were taken, doctors said the bulk of the casualties were women and children, most suffering from lacerations.
Farag, too, was there. He was searching for his wife.
"I asked everywhere, there is no trace of her," he said, his face masked with anguish. "I think she was blown away to pieces and they cannot even find her corpse."
Eyes filling with tears, he recalled how he had told his wife that he was tired, and asked her if they could skip the service.
"But she told me not to give in to my weakness, and insisted we go to the mass today," he said Farag, as he sat with other family members.
Nearby, Muslims and Christians gathered, some to donate blood, others to comfort their loved ones and check on the injured.
In a wheelchair near the hospital entrance, 65-year-old Tanay Gobraiel was one of the fortunate ones. She had attend the mass with her daughter and her cousin, Suad Atta.
"Only two benches separated me from my cousin Suad," said Gobraiel. "She was in the front bench near the altar, and I was seated two benches behind her. She died, while my daughter and I were only injured."
Suad, also 65, had insisted on attending the mass to commemorate her late husband. Sunday was the first anniversary of his death.
As darkness enveloped the city, nearly eight hours after the bombing, Farag finally found his wife. She was in the intensive care unit of the hospital, battling for life.
