The unprecedented exodus underscores how sectarian divisions that festered under decades of Hosni Mubarak's rule are taking a turn to the worse, complicated by the problems of post-revolution Egypt, a country where 10 percent of the population are Christian.
Police forces have been weakened and often don't carry out their duties. Islamists have been emboldened, with rhetoric fanning hatreds. In an atmosphere of lawlessness, Muslims and Christians alike feel freer in unleashing prejudices that in the past were kept barely under the surface.
Most notably in Dahshour, police did nothing as tensions spiraled following the burning of the Muslim man late last month.
While the man clung to life for several days, Muslim residents openly threatened to retaliate against all Christians. When the Muslim died Tuesday, the only solution from police was to encourage or assist in removing the Christian population before the violence erupted that night, Christians say. During the rampage, security forces acted to stop the crowd from storming the church, firing tear gas.
"What is grave this time is that violence was not only expected but preventable, and security forces failed to prevent it even though they had prior knowledge," said Hossam Bahgat, head of the Egyptian Initiative for Personal Rights, which monitors sectarian violence.
In the past, incidents of sectarian violence in Egyptian towns often took a routine course. A local spat between a Muslim and Christian would escalate, and if a death occurred, violence would be sparked. Police would often see a bit of unrest as a way to let off steam but then negotiate a compromise solution over the death. Officials would deny any sectarian nature to the conflict.
In recent years, there have been cases where a whole Christian family was ordered by authorities to leave their hometown to prevent retaliation. At the same time, Christians have become more ready to use violence as a preventive measure when they fear they will be attacked, said Bahgat.
But uniquely in Dahshour, angry Muslims treated the entire Christian community as the family of the accused killer and subject to retaliation.
"Collective retribution is the most dangerous and most likely (form of violence) to spread over time ... beyond the site of violence," said Bahgat.
Egypt's new president, Mohammed Morsi of the Muslim Brotherhood, didn't comment on the violence for several days. On Friday, he appealed to Dahshour's Christians to return home, promising justice against perpetrators of the violence. But, echoing the line that Mubarak's government always took for Muslim-Christian violence, he denied the incident was sectarian.
"This was an individual incident and its origin is not about Muslims and Christians, and it happens every day. It was blown out of proportion," he said. Morsi's spokesman denied the eviction was forced.
The village of 15,000 is tucked between several of Egypt's most stunning ancient pyramids and surrounded by picturesque palm groves. Security trucks are now deployed on its winding, unpaved narrow roads to guard the church and empty Christian properties.
Many in the village say the Christians should not be allowed to return until the Christian laundry worker who set fire to the Muslim is killed. Some residents take an even harder line and say they shouldn't be let back at all.
The sentiments were on display even in the neighboring Muslim family that took in Wehba to protect her in case of further reprisals.
Um Mohammed, the 65-year old matron of the household whose son was a friend of the slain man, says Christians can come back, but only if justice is served against the killer. "He burned my heart. He must also be burned. It is retribution," she said.
"No Christian will return to this village again!" someone shouted from behind Umm Mohammed. It came from a little girl wearing a strict version of the Islamic headscarf, covering her head and much of her torso. The girl - apparently the child of a neighbor - was quickly shushed and hustled out of the room by the family.
"We didn't kick them out for nothing," said Ali el-Gizawy, a 47-year old government employee. "They betrayed our trust, and they will not be allowed to return."
The Christians feel a mix of frustration at the incompetence of authorities, a sense of injustice and a fear their fate may be irreversible.
Kirollos Shehata, a 22-year old Coptic Christian resident, said he hadn't wanted to leave but finally did as his Muslim neighbors and his own departing family members urged him to go with the others to avoid more violence.
"Now I can't imagine going back," he said. For him, it's not fear of violence but a sense that the Christians humiliated themselves by leaving. "How would we look to the rest of the community and how will people treat us?" He spoke on condition his current location is not revealed.
The dispute began when the laundry man, Sameh, burned the shirt of his Muslim client, setting off an argument first with the client's wife and then with the client himself, according to several residents. The argument turned violent. On July 26, an angry crowd gathered outside Sameh's home, and he and his family lobbed firebombs down on them from his roof.
One man in the crowd, 27-year-old Moez Mohammed, was set aflame and was hospitalized with severe burns.
The next two days, Mohammed's brothers and friends went down the village's main Christian street, waving firebombs and threatening violence, said Shehata. When one Christian countered that the whole community was not to blame, a fight broke out, until it was broken up by neighbors.
"They said if you don't leave the village, you will all die," recalled Shehata. Aside from the anger over the young man's death, there was economic jealousy because local Christians are seen as better off, he said. Moreover, some Islamists used the occasion to ignite deep-seated biases against Christians and their local priest and settle scores.
Among the Muslims, stories of Mohammed's death circulated and grew more gruesome in the retelling.
"His eyes were on fire," said a young boy in the house where Wehba was a guest. "He ran like a ball of fire," said the boy's grandmother. Another described his skin melting. Some said Mohammed had tried to break up the fight between Sameh and his client over the shirt; other said saved a little girl from the fire before he caught flame himself.
Meanwhile, Christian families began sending women and children out of the village, said Shehata.
When Mohammed died on Tuesday, those still there left and police escorted the priest out. After Mohammed's burial in the evening, hundreds of Muslims began attacking the homes Christians left behind and tried to storm the church, located inside the priest's house.
Wehba, the elderly woman who lives alone in her family home, was forgotten in the confusion.
"She is like one of us," said Umm Mohammed, her host, adding that she sleeps next to Wehba to reassure her. "She has no one. And she has nothing to do with it."
Intellpuke: You can read this article by Associated Press Writer Sarah El Deeb, reporting from Dahshour, Egypt, in context here: www.guardian.co.uk/world/feedarticle/10373739