Members of the Mara Salvatrucha gang (MS-13) stand behind bars in a cell at a detention centre in San Salvador. Photo / Getty Images
Carlos holds his bare feet, cut and bruised from the harsh concrete floor, as he sits in his cell in the Tonacatepeque juvenile detention centre, just outside El Salvador's capital, San Salvador.
The 16-year-old serving a seven-year sentence for murder in one of the world's most dangerous cities speaks quietly and without making eye contact.
"My mum just got up one day and left for the United States. I was nine years old," he says.
Carlos belongs to what the United Nations has called the 'lost generation'. Across El Salvador, Honduras and Guatemala, Central America's so-called Northern Triangle, hundreds of thousands of children live without their parents on the streets or in care.
Those parents who haven't been killed or detained left their country in search of a better life, joining waves of migrants northwards. Donald Trump's pledge to shut them out using a "big, beautiful wall" has seen the largest ever 'caravans' march towards the US.
The seemingly intractable row over the wall's funding ended abruptly last month when Trump lost patience and declared a national emergency to start work on the pet project that riles his base and embitters his rivals.
Two thousand miles from where the barrier will stand the lost generation grows.
The government of El Salvador says around 500 children and teenagers are abandoned each year in the country. The Agency for the Development of Children and Adolescents (ISNA) estimates a third of these are left behind by parents, who migrate to find work in the United States.
"Sometimes the children are left completely alone to fend for themselves, but more often, they are left in the care of relatives, family friends or neighbours," says psychologist Cecilia Zepeda. "The problem is that often the people left in charge of the children don't care for them and stop providing or showing affection, and that's where problems can start."
Of the twenty inmates sharing a wing with Carlos in the Tonacatepque prison, where the fresh paint fails to conceal the overwhelming stench of stale urine, the vast majority said they grew up without a mother or father figure.
"I lived in a car park and had to beg or steal to eat," says Carlos, welling up as tears drip onto his feet. He's not ashamed, even in front of his fellow prisoners.
"People always ask where my parents are. I never knew my dad, but each time I answer this question, it's like my mum leaves me alone all over again. I wish I knew where she was."
The children and teenagers, who grow up in the absence of their parents, become easy prey for exploitation and recruitment by the rival MS-13 and 18 Street gangs, which control marginalised communities across the Northern Triangle.
Residents are held hostage by "invisible borders" that define gang turf. Trapped in their neighborhoods, they are unable to move freely, and crossing into rival territory nearly always carries a death sentence. People become victims of elaborate extortion rackets, forced to pay monthly fees to gangs, or face execution.
Carlos said he had been planning to go to Houston in Texas to find his mum, but he had joined MS-13 before he could save up enough money. He said he soon came to believe in la causa or the cause, which gangsters describe as death. Carlos said he has killed more than 20 people and committed rape. He was imprisoned two years ago.
"I started running errands for them and keeping watch for police patrols, but then as I got older, I became properly involved," he says. "But they looked after me. I had a bit of money and somewhere comfortable to sleep. They became my family."
The Northern Triangle consistently ranks as one of the most violent places in the world. Many of the tens of thousands of migrants who have fled Central America for the US say they are escaping the region's bloody gang conflict and the poverty which underpins it.
The Department for Homeland Security says 49,000 unaccompanied children were apprehended at the US border last year, and according to the UNHCR, roughly half of the children who flee El Salvador and Honduras say they are travelling to the United States to reunite with their parents or other loved ones.
Last October, the Trump administration cut aid for Central American countries because they have been unable to reduce the flow of migrants. Finding a political solution to the structural causes of violence is now one of the Northern Triangle's biggest challenges, and in El Salvador, president-elect Nayib Bukele, thinks he has the answer.
During his victorious campaign earlier this month he pledged to open more schools and said he had signed a contract with the Spanish football league to create youth training academies across El Salvador.
While mayor of the country's capital, between 2015 and 2018, the city's murder rate was cut by 16 per cent. Bukele's supporters say this was largely achieved by providing more recreational facilities in the poorest communities. But Lilia Ivett Padilla, who worked on some of Bukele's social programmes, is not convinced.
"It's not as simple as football pitches and tennis courts because the gangs eventually just destroy them," she says. "It's about being in the middle of the community and working with vulnerable families."
Ivett Padilla is director of FUSALMO, an organisation which works with children and teenagers at risk of exploitation and recruitment by the gangs. At Las Margaritas school in Soyapango, one of El Salvador's most dangerous cities, psychologists from FUSALMO work together with pupils and families as part of a structured seven-month programme.
Sixteen-year-old Julio José, whose father used to beat him and his mother, has been registered with the scheme for four months. "My mum left to work in the USA four years ago so she could escape my dad. That's when my dad kicked me out and it's when the gangs first came for me," he says. "But these sessions have helped me realise I'm not on my own and that I don't need to join a gang to belong."
Julio José is now in the care of his stepbrother and along with his grandmother they attend monthly counselling sessions.
"Children who have been left alone can become very independent very quickly. And that can actually be a bad thing," says psychologist, Ariela Arteaga. "They think they have to face the world alone and it can make them angry. We work with the whole family to try and provide structure and cohesion for everyone."
Such prevention schemes are surprisingly unusual in the Northern Triangle, where authorities have favoured more punitive and extraordinary security measures against gangs.
In El Salvador the government says the 15 per cent reduction in the murder rate between 2017 and 2018 is a direct result of its so-called 'iron fist' or mano dura policies of mass incarcerations and harsher prison conditions. But a sharp rise in murders in January and the killing of at least 11 police officers in the first two weeks of 2019 is a stark reminder of the gangs' ability to wage violence at will and create political pressure for those in power.
"It's widely acknowledged that hardline approaches don't work in the long run. There has to be a combination of strategies, including social and rehabilitation programmes in order to cut levels of violence," says José Miguel Cruz, an academic from Florida International University, who researches gangs. "The problem is that the government is not serious about rehabilitation. You just need to look at how much it spends on rehab to notice that," he says.
But rehabilitation is both difficult and dangerous. Turning to God is the only accepted method for leaving the gang. Those who simply try and leave or give up of their own accord are executed. A less common way is through negotiation to become calmado or "calmed down". But calmados do not completely leave the gang. They must still carry out errands and usually must pay extortion.
At the prison in San Francisco Gotera, which still bears the scars of heavy bombardment from El Salvador's civil war, the Yo Cambio or I Change programme has been running for over a year. Here inmates have denounced the gangs, have committed to becoming an evangelical Christian and have agreed to participate in skills and crafts workshops aimed at improving their employment opportunities. In return, sentences are shortened and visitor rights and other privileges are granted.
Each day here begins and ends with prayer and bible class. At 11am each morning and again at 2pm, prisoners gather in the sweltering heat for a sermon in the central courtyard. They each clasp a bible as if their lives depend on it. Their favourite passages are clearly marked.
There are deafening and disturbing screams as the inmates attempt to cleanse their souls and find some kind of salvation. Men who were once rival gangsters, and some of whom have committed the most heinous murders, hug each other and hold hands in a surreal display of apparent spirituality. Their heavily inked faces, where each tattoo symbolises one of their murder victims, are wet with tears as they cry and beg for forgiveness.
The prison governor says the scheme has been overwhelmingly successful. Oscar Bermúdez told The Telegraph that of the 200 inmates who completed the programme and were released last year, 67 found jobs with their new skills and 45 rejoined the gangs. Critics remain skeptical, however. Those who refuse to engage with the religious teachings are locked in solitary confinement because they destabilise the prison, according to the governor.
"There's no doubt that some gangsters genuinely find God," says Dr Cruz. "But many also use it to get more lenient treatment. Most end up using it as a façade."
In Tonacatepeque, where there is no formal rehabilitation programme, Carlos makes eye contact for the first time.
"I want to work with computers, but I don't think I deserve a future after what I've done," he says. "I think my future will be an early death, like it is for most gangsters."
It comes after the US recently struck nuclear sites in Iran.