A 17-year-old boy, who requested anonymity for fear of reprisals, recalled the scene outside the Sufi mosque as the massacre began. "I saw a man in army uniform," he said. "He opened fire on us. The bullets were ricocheting off the walls, hitting people in the legs and back."When the attackers left, he went inside to search for his father among the dead. "He was on his side. It looked like he was shot up close in the head when he was already down," he said.He and others who spoke to CNN said the entire incident lasted roughly an hour.Mohamed, another eyewitness who asked CNN to refer to him only by his first name for his safety, was at another mosque down the street when he saw several four-wheel vehicles driving up to the al Rawda Mosque. "I heard shooting and screaming and shouting, so I ran toward the mosque. I saw four people I know who work for the army, and they were firing at the attackers, but they ran out of ammunition. One of them, Ahmed, was killed after he finished his ammunition."According to the official narrative, the death toll from the attack, the bloodiest in modern Egyptian history, stands at 305, including 27 children.These accounts, as well as the video and still photographs in this report, were provided by CNN's Sinai stringer, Mona El Zamlout. For several years, Egyptian authorities have barred CNN and all other international news organizations, as well as most Egyptian news media, from entering the northern Sinai peninsula.On Saturday, Egypt's Public Prosecutor issued a statement saying that the attackers arrived at the al Rawda mosque in five SUVs, some wearing combat fatigues, some masked, heavily armed, and bearing the black banner of ISIS."The ones who were masked spoke like Bedouin," eyewitness Mohamed recalled. "The ones with their faces exposed, however, spoke with Cairo accents, they were big, and had long hair."ISIS's affiliate here, known as Wilayat Sinai or Sinai Province, has yet to claim responsibility for the massacre, and may never do so, says H.A. Hellyer, senior nonresident fellow at the Atlantic Council and Royal United Services Institute. "The chatter that you've seen online, even from people that support ISIS, was quite a lot of shock and horror at what happened on Friday," Hellyer says.Friday's attack was the first time Wilayat Sinai targeted a Muslim house of worship. In the past, their violence was focused on army and police checkpoints and positions in the northeastern Sinai. In the past year, they've attacked a Coptic cathedral in Cairo, a church each in the Nile Delta city of Tanta and the Mediterranean port of Alexandria. In October 2015, the group claimed responsibility for the downing of Metrojet flight 9268, killing all 224 passengers and crew on board.Why the Sinai peninsula is so dangerous"With the Christian attacks," says Hellyer, "it seemed aimed at creating some sort of divide within Egyptian society the radical groups could then take advantage of. They failed. Now they're going after anybody that doesn't support what they want to do."It's possible that they specifically targeted the al Rawda mosque because it is affiliated with a local Sufi order, the Jaririya. Sufis are Islamic mystics and have traditionally shunned violence. ISIS considers Sufis to be heretics, and in Syria and Iraq, they have destroyed Sufi shrines and bulldozed or dynamited the tombs of Sufi saints.In November 2016, Wilayat Sinai kidnapped and beheaded Sulaiman Abu Haraz, a widely respected 100-year-old Sufi sheikh. According to one resident of the town, the militants threatened the mosque five separate times, ordering those responsible to stop holding Sufi gatherings. They refused.Another theory is that the attack was in revenge for local residents' cooperation with Egyptian security forces.Whatever the motive, the result is a town that's been shattered by mass murder. Some estimates place a quarter of the community's men dead. Until now, the town of al Rawda had largely been spared the violence that has plagued this part of the Sinai.Six of 40-year-old Salama's relatives were killed in the attack. He and his extended family had fled to al Rawda from the fighting in his hometown of Shaikh Zawaid, near the border with Gaza. "We came here two years ago because al Rawda was the safest and most peaceful town, but by God we aren't going to stay here."