This is Abu Bakar Shikal, the leader of the feared Boko Haram militant group. Little is known about the man whose gunman abducted 200 schoolgirls from the town of Chibok in the northeast of Nigeria. Filming openly in the region is dangerous, so the BBC has travelled covertly into the north of the country and has gained exclusive access to people who knew him well. Officials have been done anonymously as people are too scared of reprisals. This man was a member of what became Boko Haram, he knew Shikal personally. He is a fanatic, not well versed in Islamic law. He takes hasty decisions and is very hard line when Islamic matters. And even his former mentor was careful around him because he was not open to any form of compromise. Shikal spent his formative years here in my dooghry, a major city in the northeast of Nigeria. Even by local standards, Shikal lived in abject poverty in this house in a slum quarter of the city. Shikal later enrolled himself at this formal Islamic school run by the government. One former classmate remembers him as a loner who kept himself apart from the other students. We thought of him as psychologically affected. Just looking at him, you could tell that he was not completely with it. But Shikal went on to lead Boko Haram five years ago, instigating a wave of terror through bombings and abductions. I headed north to meet another former colleague of Abu Bakar Shikal. He thinks the international outcry over the abductions of the 200 schoolgirls will have played well with the leader of Boko Haram. He will have been pleased with all the media attention. He is happy with what they have done. He said that they will sell the girls on as slaves and has made it abundantly clear that they will abduct more girls. These haunting pictures of the schoolgirls remain the last known images of them. Since the mass abduction in April, there have been further kidnappings of women and children in the same area, and Boko Haram have killed over 500 civilians. Yaldeh Hakeem BBC News, Abuja.