When Nicolás was 17 he was forced to kill eight of his friends.
"It hurt to kill them, obviously," Nicolás said, bowing his head as his voice started to tremble. "But an order is an order. I couldn't think about that."
Nicolás had been with Colombia's largest rebel group, the Revolutionary Armed Forces of Colombia, or FARC, since he was 12. Some of his condemned brothers in arms were as young as 14. Their crimes included trying to desert, and falling asleep during lookout. One had ruined the camp's food. Burning rice is an executable offence in the jungle. Refusing to carry out the executions would have got Nicolás killed himself.
Nicolás is able to tell the tale because, a year later in April 2015, he deserted himself.
The former child guerrilla said he hasn't been able to relax since then. He talked of repeated threats and having to keep his previous life as a rebel secret. After communicating via intermediaries for months, he was cautious, always scanning the room to see who is listening. Dressed in jeans and a t-shirt, rather than the military fatigues he wore for years, he looked fresh-faced and vulnerable. He insisted that we use a fictitious name to tell his story.
The FARC is one of the main protagonists of Colombia's half-century-long armed conflict that has killed over 220,000 people, mostly civilians, and displaced an estimated six million. Other rebel groups and, above all, state-aligned paramilitary groups and the state forces themselves, have all contributed to the bloodshed. Atrocities have been committed by all sides.
The seemingly imminent peace deal between the FARC, which was formed in 1964 and is currently the biggest remaining rebel group, is a watershed moment for Colombia at a time when many are reflecting on the cost of the country's long war.
Some of those who have paid dearly are the children who have fought in the conflict.
'It hurt to kill them, obviously... But an order is an order. I couldn't think about that'
Earlier this year the government's Unit for Attention and Reparation of Victims had documented the cases of 8,942 children recruited by armed groups since 1985.
One Colombian military intelligence source said that rebels, such as the FARC, found recruitment easy where local communities had little experience of the state other than "bombs and bullets."
Nicolás was recruited before he was even a teenager. He was living with his family in Putumayo — a rural but resource-rich department in the jungle on the country's southern border with Ecuador, and long a rebel stronghold owing to the presence of oil companies, which the group regularly required to pay protection money.
"They would recruit in all kinds of ways," Nicolás said, fidgeting uncomfortably. "They were everywhere. They had people in the schools."
His elder sister's fiance, a FARC insurgent, handled his recruitment.
For Nicolás, and many others, a fractious and impoverished home life made joining the rebels easier. He left one day without saying goodbye. Only his sister knew where he was going.
'They would recruit in all kinds of ways... They were everywhere. They had people in the schools'
"I wanted a new family, away from my father and stepmother," he said. "I liked the camaraderie and the friends I made."
Recruiting children under the age of 15 to "participate actively in hostile activities" is a war crime according to the International Criminal Court. The United Nations sets 18 as the minimum age for participation in an armed conflict.
Figures released by Colombia's family welfare institute indicate that about 6,000 children have disengaged from armed groups over the past 17 years, with 60 percent of them belonging to the FARC.
As part of ongoing peace talks, the FARC announced on Sunday, in a joint statement with the government, that it would soon be releasing all children aged 15 and under from its ranks. The statement promised a "roadmap" for the release of older minors, and a special program to attend to them all.
The statement also contained a pledge by the government to define the younger group of former combatants as "victims" of the conflict who would consequently not face any charges for crimes they might have committed. It said rebels who are currently aged 16 and 17 will be pardoned for "rebellion," although they will not escape special post-conflict trials for more serious crimes, such as rape or murder.
Earlier in the peace process the FARC had promised to halt the recruitment of children, though this is the first time a bilateral agreement has been reached on how to release those already in the camps.
'Once you're in, all you learn about, outside combat, is Marx and communism... Everyone believes in it'
Nicolás was recruited to the FARC's 32nd Front, based in Colombia's dense southern jungle. The front is responsible for carrying out attacks against mining infrastructure, in part to alert authorities to their presence, and in part to extort protection money, known as vacunas or vaccines.
"I saw it happen. Briefcases of cash, all Colombian pesos, handed over from a company guy to one of our more senior fighters," he said, his eyes darting around the room. "If the contract was for 10 million pesos (about $3000), the vacuna would be 4 million."
But it wasn't just about oiling finances. The FARC also inculcated young recruits with the teachings of the classic left-wing revolutionary ideology that has underpinned almost all guerrilla movements in Latin America since the 1960s.
"Once you're in, all you learn about, outside combat, is Marx and communism," Nicolás said. "Everyone believes in it."
After being with the rebels for a year as a miliciano, or support troop, he said he was promoted to guerrillero, a fully-fledged member of the guerrilla. That brought training in explosives and communications. From then on, he said, promotion was swift.
At 15, Nicolás said he was a troop leader, in charge of 16 people. Then at 16 he was head of his unit of 30 people. At 17, he became a representative of his company, responsible for 64 fighters. During this time he was also a part of the front commander's security team. Observers have commented that the FARC leadership often promotes young recruits particularly quickly, as a means of giving them a perceived stake in the organization.
Nicolás said that his own desertion, at the age of 18, was aided by the knowledge his position of responsibility had given him about his location in the jungle.
After waiting for a particularly rainy night — so the sound of raindrops against the tents would disguise footsteps — he fled along with two friends, though he has since lost contact with both. He said he had to free one of them who was tied to a tree for having previously tried to desert.
'There may be peace talks going on, but to them, people who desert are still sapos'
"I stopped believing in it all," he said, remembering his decision to go and visibly troubled with a slight quiver in his lips. "I spent all that time living something I no longer believed."
In the year since he deserted Nicolás said he has made sure none of his neighbors know how he spent his adolescence. Meanwhile, he said, he has received death threats from FARC rebels, but they haven't tracked him down beyond his cellphone number.
"There may be peace talks going on, but to them, people who desert are still sapos," he says, using the Spanish word for toad and for traitor.
Looking back on it all, Nicolás highlighted the discipline of life in the rebel ranks. Despite the camaraderie and rhetoric of social justice and equality, the front commander was never "a brother" and always "a boss."
"You can't sleep easy in the guerrilla. You can't dance, you can't play, and you can't talk with your family," Nicolás, now 19 years old, said of the six years he spent as a rebel. "That's where my youth went."
Nicolás also talked about the requirement to get permission from superiors before starting a romantic relationship.
'You can't sleep easy in the guerrilla. You can't dance, you can't play, and you can't talk with your family... That's where my youth went'
Women make up about a third of the FARC's fighting force but pregnancy is forbidden. Nicolás said that contraceptive hormonal implants were available but that some rebels, many of whom have almost no education, didn't understand when they were effective. He also confirmed long-standing reports that pregnant combatants were forced to have abortions, even very late ones, something the FARC has long denied.
"If they have a baby they won't want to stay," the ex-guerrilla said. "So they make them have an abortion and they stay. They do it six or eight months into the pregnancy."
'Crying is forbidden... Crying says you're not loyal to what you're doing'
Nicolás also spoke of the pressure on combatants to put on a front of emotional stoicism at all times.
"Crying is forbidden," Nicolás explained, wiping his brow. "Crying says you're not loyal to what you're doing."
So Nicolás said that when he got upset about something he tried not to think about it, and he didn't cry.
According to a 2012 report by Colombian doctor Natalia Springer, the prohibition on crying has a particular impact on the moral compass of child soldiers, as it stops them asking about the pain caused by the violence they are participating in.
Now, as peace talks rumble on and a final accord is all but guaranteed in 2016, the FARC have been keen to distance themselves from their most blood-curdling abuses. In December the rebel leadership apologized for a massacre in the western Chocó department that took place in 2002, the first time the group has publicly accepted responsibility for civilian bloodshed.
The agreement that child soldiers will be released from rebel ranks was also described in Sunday's joint statement as a "trust building measure." But what is said at the negotiating table does not always apply to the jungle.
'Kids in the countryside love guns. And a lot them won't hand them in... It's the reason they joined'
Nicolás said that the group was still recruiting kids as young as 14 or 15 when he deserted last April, three months after the FARC had announced it would stop recruiting children under 16 years old.
Human rights groups have also noted that recruitment of minors has continued since last year's promise that it would stop.
The military intelligence source said he believes that such recruitment could be motivated by a desire to swell the rebel ranks ahead of its conversion into a political party. But whatever the reason, Nicolás said it is always dangerous to train children how to use weapons they might be reluctant to hand over once the peace is signed.
"Kids in the countryside love guns. And a lot them won't hand them in," Nicolás said. "It's the reason they joined."
Such statements feed fears that many demobilized rebels will join other armed groups or criminal gangs.
Olga Acevedo, who works with the NGO War Child in Colombia to protect children from conflict, said that reintegrating child combatants back into society will probably be particularly difficult given the lack of opportunities.
"If they can't get an education, then it is always tempting to join an armed group," she said.
Nicolás gave no indication he was tempted to return to arms, but his story did suggest his own reintegration has been hampered by the fact that so many Colombians distrust the rebels. It also appeared to confirm the warnings of some peace workers that rebels also find it hard to trust civilians.
"These people have lived most of their lives in fear," said Liduine Zumpolle, director of Manos Por La Paz. "They don't know how to trust in anyone."
Follow Joe Parkin Daniels on Twitter: @joeparkdan