When Daesh militants started shooting, Mushin closed his eyes. It was August 2014 and he was standing next to his father and brothers. They were lined up with more than 80 other Yazidis from Kani, a village in northern Iraq. He fell into a grave and for a few minutes thought he was dead. But he wasn't, he only had some superficial wounds. He checked on the others, and realized he was the only survivor. He waited 20 minutes, and ran. That same day, another of Mushin's brothers, Ismail Maajo, crossed the border into Turkey, fleeing Daesh's advance across his homeland. News quickly reached him of the attack on the village. "Those were terrible hours. I didn't know what to think. I just wanted to get back, hoping to find somebody still alive," Maajo told the Thomson Reuters Foundation. In the summer of 2014, Daesh fighters swept across northern Iraq, capturing most of the territory between Syria and the Iraqi city of Mosul. As the militants overran the town of Sinjar, home of the ancient Yazidi community, they systematically killed, captured or enslaved thousands of Yazidi men, women and children. United Nations investigators last week declared that Daesh is committing genocide against Yazidis in Iraq and Syria. Of the 36 members of Maajo's extended family, 31 were captured or killed by the militants. Twelve remain in captivity. "At least I know where my father and brothers are. I went to see the mass grave" where their bodies were dumped, Maajo said by phone from his new home in Nebraska in the United States. But the extent of the Sinjar massacre is still unclear, and Yazidi campaigners are undertaking the grim task of documenting mass graves in an effort to piece together an accurate record of the atrocities. COUNTING THE DEAD "We counted nearly 40 mass graves, but one third of the area is still under Daesh control, so there could be more," Haider Elias, president of Yazda, a Yazidi support group based in Dohuk, Iraq. New sites are unearthed almost every day. Andrew Slater, the supervisor of Yazda's documentation team that collects evidence by talking to witnesses and inspecting sites they can safely reach, said identifying all the graves will be a monumental task. "There are hundreds of places throughout the Sinjar area where we have discovered one, two or three bodies. This is why is so difficult to have an official count," Slater said by Skype from Dohuk. "And I think there are many mass graves we have not seen in IS-controlled territory." The Yazidis are a religious sect whose beliefs combine elements of several ancient Middle Eastern faiths. Daesh has tried to erase the Yazidis' identity by forcing men to choose between conversion to Islam and death, raping girls as young as nine, selling women at slave markets, and drafting boys to fight, last week's UN report said. In some villages around Sinjar the killing was systematic. In others it seemed more random. The militants exploited religious divisions to turn communities that had lived together in peace for decades against each other. This was the case in Hardan, northeast of Sinjar, a village of some 2,000 Yazidis. As Daesh advanced, elderly residents from Gumez, a nearby Sunni Arab village, went to Hardan and advised the men to drop their weapons. They convinced them that if they didn't fight, they would be spared. Some people fled, others remained. When Daesh militants arrived, they divided the men from the women and children. About 300 men were brought to the intersection with the main road that runs to Mount Sinjar. By sunset, they had all been executed, locals from Hardan told the Thomson Reuters Foundation. CRIME SCENE Nearly two years on, bullet casings still litter the ground at the execution site, rusted by the rain and wind. The mounds of bodies are partially covered by earth and grass but a closer inspection reveals fragments of clothes and body parts. Kurdish forces recaptured the area in November and fences have been erected around the graves and with a sign reading ‘Crime scene: do not enter'. "We are working to protect these sites, too many people entered and touched what they shouldn't have," said Fawaz Abdulameer, deputy head of mission for the International Commission on Missing Persons (ICMP) which tackles the issue of people who are missing as a result of conflict, human rights abuses, disasters and organized crime. "We asked for soldiers to guard them, but nobody has yet arrived." The designation of the Yazidi persecution as genocide has provided a "road map for prosecution," U.N. investigator Carla del Ponte said last week. Yazda has already taken steps to open a case with the International Criminal Court in The Hague, while campaigners also hope that a local court can be established to prosecute the perpetrators of violence. "Too many people in this area supported those criminals (Daesh) and we don't want families to feel their rights have been taken away from them," said the ICMP's Abdulameer. "The purpose of our work is to bring justice. Without justice there can't be any peace, and without peace we will not be able to live together anymore."