No-one would ever think that a few months ago this 18-year-old was arrested wearing a suicide vest, hours before he was to blow himself up at Kohat University in north-west Pakistan.

Gul was at school in Kohat, a city in Khyber Pakhtunkhwa province. During the summer holidays, he would visit his ancestral village in a tribal area near the border between Pakistan and Afghanistan.

It was in that volatile territory that one of his cousins connected him to the militants and he was recruited for training.

"They [the militants] used to give us lectures [saying that] according to Sharia [Islamic law] it is obligatory to pursue jihad [holy war] against the government now. I lost my mind and started believing them. They lectured me for three months," says Gul Khan.

He tells me his story from a centre established by Pakistan's army in the town of Tank, close to the border with Afghanistan, for the rehabilitation of young men who supported and sympathised with militants.

One of three such units in Pakistan, the centre is protected by tight security. But inside there are classrooms for vocational training, a basketball court, a TV room and a mosque.

Gul Khan underwent militant training with around 12 others at a camp in the Orakzai tribal region. His parents were completely unaware of this radicalisation until his last trip to Kohat.