Though Santiago felt sorry for his former compatriots, he mostly felt devastated that years of work — building alliances and trust in civil society, forging relationships with rivals, selling the vision on the streets — had been turned into a public spectacle. But he had his own problems to worry about. By the end of August, even before the defendants were found not guilty, he was already preparing to flee the country.

Santiago knew there would be no reprieve, at least not until the 2018 elections. Well before the trial, Santiago wrote a manifesto for the gangs. For the first time in decades, they would not support the F.M.L.N. at the polls. They would instead use their political might to swing the elections away from them, whether to the right-wing party or, potentially, third-party candidates. The quid pro quo had always been support — in return for money — for the F.M.L.N. But President Sánchez Cerén of the F.M.L.N. had broken its longstanding relationship with the gangs by waging war against them. So the gangs would respond by wielding their 10 percent of the vote to punish them in the Legislature. The approaches from political parties had already started: politicians seeking access, favors, votes ahead of next year’s election. “We are the pretty girl that everyone wants to dance with right now,” Santiago told me.

But they would do so without Santiago. The authorities had found him. This February, months before the trial started, he was pulled over for a routine traffic stop after another meeting with Bishop Gómez. The police ran his car and identification, then let him go. But Santiago was suspicious. He sent his car to a specialist who found a GPS tracking device stuck to the chassis. Santiago switched vehicles.

In April, shortly after Easter, the police stopped him again. This time they charged him with resisting arrest and placed him in detention. After four days, two prosecutors and a police investigator came with an offer. The truce trial was a few months away and Santiago could testify against his former compatriots or he could go to jail for the rest of his life, on possible charges of gun trafficking, electoral fraud and smuggling contraband into jails. After making the offer, the authorities were forced to let him go — they had no grounds to hold him.

But he knew they would arrest him again, and he would be faced with the same dilemma. He didn’t want to snitch and undermine what he genuinely believed was the only way out of the cycle of violence consuming El Salvador. It would be turning his back on everything he’d worked for and all those he had tried to convince. At the same time, with the prisons teeming with disease and overpopulation, he couldn’t imagine being consigned to a shared cell for the rest of his life. He was only 34. He decided to flee.

When we last spoke, he would not tell me where he was, only that he had no plans to return to El Salvador, at least not for the next year or so. He was no longer the optimist of even six months earlier. The F.M.L.N. would lose the presidential election in 2019. And his people, the gangs and their community, would ensure they had a tough time in next year’s legislative and municipal elections. But in the meantime, he could do nothing to further the cause of dialogue. For now, that effort was broken.

“Right now, I’m a bit more of a realist,” he said. “I could argue that no matter which party wins, they are not going to look for an alternative.” The civil war took years and tens of thousands of deaths to push both sides to negotiate. So, too, would this war. Wars only end when someone wins or when both sides grow tired of the killing. “The violence has to reach a much higher level than where it is now to force that reckoning,” he said. “Only then will people start thinking about an integrated solution. The truth is, the country has to bleed more.”