In early April a suicide blast ripped though a Pakistani shrine packed with thousands of devotees, leaving scores dead. Both attackers were schoolboys in their early teens. But one survived and told the BBC's Aleem Maqbool what made him want to take his life and the lives of others.
"All I was thinking was that I had to detonate myself near as many people as possible. When I decided it was the right time, it was a moment of happiness for me," said 14-year-old Umar Fidai.
"I thought that there would be a little bit of pain, but then I would be in heaven."
Umar did not make it to paradise. Instead, we find him in custody.
His left arm is missing, his right arm entirely strapped up, and there are bandages around his torso. But he is alert, polite and disarmingly frank.
"The plan was that Ismail would blow himself up near the shrine. I would wait for the ambulances to come and detonate myself near them to kill more people. I had no doubts at all beforehand."
But Umar's suicide jacket failed to explode properly.
He blew off his own arm, tore open his abdomen and was knocked unconscious. When he came round, Umar reached for a grenade in his pocket.
"We had been taught that if the belt does not go off, we should kill ourselves with the grenade. There were three policemen standing close by, and I thought if I killed them too, I would still make it to heaven."
As Umar raised the grenade to his mouth to pull out the pin with his teeth, a police officer shot him in the arm.
Extraordinary mobile phone footage shows Umar lying on the ground as police then went about defusing the remains of his suicide jacket.
'Taliban all round'
His journey to get to this point had started five months earlier, in his hometown in the mountainous tribal regions of north-west Pakistan, close to the Afghan border.
"Where I used to go to school, there were Taliban all around. One day one of them told me to go with him to become a suicide bomber, but I told him if he wanted to kill people he should do it himself, not ask children. But he kept coming back.
"He said there was no point studying. He told me that nothing was better than paradise, and that you could earn that by killing non-believers.
"The Taliban prayed all the time and read the Koran, so I thought they were good people. My heart told me to go and train with them."
Umar said he was blindfolded and sometimes handcuffed when he was taken to the training compound, so he would not be able to reveal its location.
He said he was trained in the use of weapons and explosives with three other boys.
Thousands of Pakistanis have been killed in militant attacks in the past three years.
It is thought that the majority of suicide bombings are now being carried out by children like Umar, trained by the Taliban.
The targets across Pakistan have been diverse, but several recent bombings have been at the shrines of Sufi saints, like the one Umar was involved in.
These shrines have long been a focus of devotion and prayer, but hardline Islamists have decided that worship at them is un-Islamic.
"The Taliban always told us we would go to Afghanistan to kill non-believers," says Umar. "We agreed, because they said that would mean we would go to paradise.
"But when we travelled by bus to the place of our attack, I saw it was still Pakistan so I questioned them. They said the people who pray to the dead at shrines are even bigger infidels, and I believed them.
"When we got to the shrine, Ismail and I went up a hill to a place nobody could see, took our suicide jackets out of our bags, and put them on.
"Then we said our goodbyes and promised we would pray for each other, but we were not sad, because we thought we were going to heaven."
Umar said it was only when the police were trying to defuse his explosives and when he saw the care the doctors were giving him, that he started to realise he had been wrong.
"I am so grateful, because I have been saved from going to hell. I am in a lot of pain, but I know there are many people in hospital even more severely injured than me and I am so sorry for what I did and for what Ismail did.
"We did a very bad thing by killing children and old men and women. I now realise suicide bombing is un-Islamic. I hope people will forgive me."
Umar told me that nobody from his family had got in touch with him since the attack
"I know my mother and my younger sisters, in North Waziristan, would know what's happened and they must be very upset. I just want to apologise to my mother. But at the time I detonated myself, thoughts of my family were not in my mind, I was only thinking about what the Taliban had taught me."
The attack could still cost Umar his life, he remains seriously ill.
He is also now scared that the Taliban could come to kill him at any time for failing in his suicide mission.