Fifty-one dead at dawn. A doctor who said he preferred not to give his name lives in an apartment building that overlooks the Republican Guard barracks in Cairo. He told me he woke for the dawn prayer before 4 A.M. Shortly afterward, he heard gunfire and went onto his neighbor’s balcony for a better view.

“I saw that the Army retreated about ten metres and began to fire tear-gas cannisters, about ten or fifteen of them,” he said. “I couldn’t see if the other side [the protesters] was shooting, but I heard people through megaphones encouraging jihad. Then I saw four to six motorcycles coming from the direction of the Rabaa intersection to the Republican Guard barracks. Some people were still praying, some were not, because the dawn prayer had finished by then. The men on the motorcycles were all masked, and it was hard to see them through the dark and the tear-gas smoke, but they seemed to be shooting, they were coming from behind the protesters, so they were shooting toward the protesters and the Army. Then the Army started firing. And the protestors were firing. I saw firing from both sides.” As for details, though—what they were firing, whether it was one or two protesters or something more organized—he said that it was dark and that he couldn’t exactly tell.

The Islamists remained adamant that the Army fired on peaceful demonstrators. The Army says that they were provoked. Although many eyewitnesses and video clips corroborate some details—tear gas was fired by the Army at the start; gunfire came from at least some people on both sides, even if the Army did most of the shooting—there’s no clear indication of what sparked the violence. It is clear, however, that the vast majority of fatal injuries were caused by live ammunition, and that most of the dead were protesters. (An Army officer, a policeman, and a soldier were also reported killed.) Over the past two and a half years in Egypt—melee and propaganda and obfuscation—it has always been nearly impossible to separate fact from conspiracy theory and actual conspiracy. Crowds are routinely seeded with paid thugs and provocateurs, guns have become much more prevalent, tensions and emotions are raw and ragged.

The doctor has been living inside the cordon around the sit-in for the past three days. He went out to protest on January 25, 2011. He voted for Mohamed Morsi, because, he told me, although he didn’t think any of the Presidential candidates were that great, he thought the Brotherhood was the best organized party and Morsi “the safest choice.” Disillusioned, he went out again to call for Morsi’s removal and early elections in the mammoth demonstrations on June 30th. He told me that he thought some of the protesters were down-to-earth and decent men; others, he felt, were “full of hatred and poisonous ideas.” Through the din and confusion of Monday morning, he could hear both soldiers and protesters calling for calm. “But the atmosphere has been charged between the two sides for several days.”

Below, he could see some people trying to take refuge in his building. He went down and treated those who were choking from tear-gas inhalation or had been bloodied with what he took to be bird shot. He said some were quiet and frightened, others were screaming invective, even accusing other protestors of being atheists because they had run away from the Army’s guns. “I told one of them, ‘But you ran away too!’ But he said he had done so because he had no support.”

The doctor said about a hundred and fifty people tried to take refuge in his building, most of them among cars in the below-ground garage. He told me he went down to the ground floor to turn on the lights in the hallways and staircases, and met several soldiers who came in looking for protesters. He felt safer when they arrived. His parents were upstairs, families were terrified, and there was a lot of chaos. The soldiers told him to put his hands on his head; he explained that he was a doctor who lived on the tenth floor, and he showed them his I.D.; they asked him to show them where protesters might have come to hide. They found one group who had broken into an empty apartment. The soldiers made them sit on the floor with their hands on their heads and searched them. The doctor said that they found a shotgun. “I told the soldiers to behave nicely, and with some people they were nice, but some protesters were calling them infidels and traitors. One of the soldiers responded angrily, ‘Did they really tell you that we are infidels? I don’t care who Morsi is, but right now you’re telling me I am an atheist and a traitor!”

The doctor escorted several soldiers to the roof. Thirty protesters had gathered there, and there was a brief exchange of gunfire between a soldier and a man who let out a burst from a large gun, then tried to hide the weapon in a water tank.

The doctor’s account is one among many. Egypt, split over the past ten days between coup and revolution, woke up today to an ever-widening rift between the two sides of this story.

On Sunday night, millions had gathered in opposing rallies across Egypt. At the Rabaa intersection in Cairo’s Nasr City, where the Muslim Brotherhood have focussed their crowds, Islamists bitterly denounced the deposition of the first fairly elected President of Egypt. At Tahrir Square, the national anthem boomed from loudspeakers as fireworks burst and disco-green lasers went up from the crowd, playing over the silhouettes of the helicopters circling overhead and dropping patriotic flyers. The roar of several F-16 flybys was sheer triumphalism, even as opposition parties met to try and cobble together some kind of national-unity interim government.

For several days, Morsi supporters have massed outside the Republican Guard barracks, believing that Morsi was held inside. On Friday afternoon, three protesters were killed in a brief volley of gunfire and bird shot. The protesters, at times several thousand, remained, chanting behind a barbed-wire cordon. In the early hours of this morning, shots rang out. When it stopped, about three hours later, dozens were dead and hundreds were injured. The fragile political negotiations for a new government faltered. The Salafist Al Nour Party withdrew from talks in protest at the Army’s actions; Mohammed ElBaradei, a mooted member of the new government, from called for an investigation.

Rumors, accusations, and mobile-phone footage flooded the airwaves and TV channels. The private cable stations have supported Morsi’s ouster, and the national-TV channels virtually ignored the footage of gunshot wounds and dead bodies laid out in a makeshift field hospital under sleeping bags and an Egyptian flag. All day, they have played a pro-Army montage on a continuous loop: a wounded soldier being carried to safety, a man in a black balaclava carrying a shotgun amid an otherwise unarmed knot of protesters, a pistol flash from behind a brick corner, bottles of whiskey allegedly found in “devout” protestor’s tents.

Along Tehran Street, where most of the clashes occurred, there were many pools of dried blood and blood trails, some marked with cardboard signs—“A MARTYR’S BLOOD”—or garlanded with bloodied clothing and branches of ficus trees that grow along the roads. The protesters were shocked and exhausted and angry. There was a palpable sense of betrayal. I have been in Rabaa for several days, and most of the Islamists I spoke to were at pains to avoid criticizing the Army. Ranks of Brotherhood even lined up to protect the gates of a military-administration building. Plenty were carrying big bamboo sticks, but I saw no guns or knives, and the atmosphere was friendly and peaceful.

On Monday morning, they were building low walls, using dug-up paving stones as bricks and as barricades. Some with bloodstained T-shirts, some with bandaged foreheads from bird shot, they gathered around any foreign journalist, holding up spent bullet casings with the initials of the Egyptian Armed inscribed on them, desperate to have their story told. People I spoke to in a smallish crowd at a corrugated iron barricade, behind the barbed-wire front line, claimed that the Army had massacred people as they prayed. “Is this the democracy the Americans called for?” “A bullet grazed the forehead of the man standing next to me!” “There were Army snipers on the roofs!” “They shot tear gas!” “This is just another military coup!”

As I listened to them, I was startled by a cracking noise that might have been a double gunshot, or might have been part of the adjacent building, which was still on fire, collapsing. Minutes later, some tear gas wafted over and a man, almost unconscious and gasping for air, was sped away on a motorcycle for treatment. Funerals for the dead went on throughout the afternoon.

Photograph by Mahmoud Khaled/AFP/Getty