Kaduna - Three years after his family fled their north-eastern Nigerian home to escape threats from Boko Haram militants, Mudasir Gambo must have thought his luck had changed when he won a ticket to attend the annual hajj pilgrimage in Saudi Arabia.But in a cruel twist of fate, the 19-year-old, who had memorised the entire Koran when he was eight, was among more than 700 pilgrims killed last month in a crush outside the Muslim holy city of Mecca.Nearly two weeks after the worst disaster to strike the pilgrimage for 25 years, more than 50 mourners were gathered at the Gambo family's modest three-bedroom house, moving by turns from a communal compound outdoors to pray inside for Gambo, who had been on his first trip outside Nigeria when he died."It was shocking. I felt traumatised, confused and very empty," said the teenager's father, Mallam Sallau Gambo, in a trembling voice. "His death has left a very wide gap that can never be filled."The crush took place as millions of people tried to reach three walls to pelt them with stones in a ritual intended to drive out the devil.Hardworking, diligent and humbleUba Mana, a spokesperson for the National Hajj Commission of Nigeria, said on Thursday that 99 pilgrims from the west African country died, 42 were hurt and 215 were missing.The haj, the world's largest annual gathering of people, has been the scene of stampedes, fires and riots in the past, but their frequency had diminished in recent years as Saudi Arabia's authorities spent billions of dollars to improve safety.Gambo's family grew concerned when he failed to call them in the evening, as he had on previous days, to discuss his movements. He had been performing the pilgrimage with his Saudi Arabia-based brother, Abubakar, before the pair were separated.After a week-long search, Abubakar found his brother's dead body in a hospital in Mina."I managed to calm his brother down on the phone, but couldn't hold back my tears," said the glassy-eyed, grieving father.The teenager's mother was said to be too distraught to discuss the death of her son, who had seemed destined to follow in his father's footsteps as an Islamic scholar."I have never met a student of his age that was so hard working, diligent and humble," said Abdullahi Abba, one of more than a dozen Islamic scholars who had gathered at the family home.Centre of the insurgencyThat same zeal earned him what seemed to be a dream opportunity. He won the haj trip, a car and a cash prize for coming second in a national competition for the recitation of the Islamic holy book."Mudasir told me to use the cash to buy land where he would build a mosque and an Islamic school," said Gambo's father, adding that the pilgrimage would have been unthinkable without the prize.His apparently bright future contrasted with the shadow cast over the family's past by Boko Haram, the militant Islamist group which has killed thousands and forced around two million people to flee their homes in the north since 2009.In 2012 Gambo's father, who supports his four wives and 28 children through farming, fled Maiduguri, the centre of the insurgency, when militants threatened to recruit his sons and abduct his daughters. Those who resisted would be killed.The threat by the group, whose name means "Western education is forbidden" in the Hausa language, was punishment for the children being enrolled in non-religious schools by their Islamic scholar father.Unanswered questionsWithin days of the threat, the family left behind their home, farmland and livestock to seek refuge at a camp for internally displaced people in the north-western city of Kaduna. They eventually secured permanent housing in the city.A few of the mourners sitting inside the near-silent family home or gathered under a tree in the compound had travelled around 800km from Maiduguri to pay their respects."My family and I feel safer here and never had any calamities until the tragic death of my beloved son," said the pilgrim's father, who wept quietly as he discussed the way his eighth offspring died, unmarried and with no children of his own.Unanswered questions remain regarding the cause of the crush that claimed his son's life. Critics of the Saudi government say the disaster may have been caused by authorities halting crowds to make way for a VIP.The dead teenager's father had heard a similar account of events. He was told that a single narrow route left for pilgrims had been blocked to allow a crown prince to perform the stoning ritual. Saudi Arabia has strongly denied this, saying police did not close the main pilgrimage routes.The Saudi authorities buried Gambo in a ceremony observed by his brother, to whom a death certificate was issued, their father said."Apart from the death certificate, no Saudi or Nigerian official has contacted or communicated with the family," he said, with tears streaming down his cheeks.