Chaftari is a member of Fighters for Peace, a small group of former militiamen from Lebanon's various sects. He and others are determined to prevent future generations from falling into violence.
The group sponsors workshops, lectures and events whenever and wherever they can, confessing their wrongdoings and showing that redemption and reconciliation are possible -- and so is war, if the roots of conflict are not openly addressed.
Chaftari never considered himself an extremist. He attended Jesuit schools, counting among his friends Muslim classmates, though he considered them different because they lived among Christians.
"I never had bad feelings about them, because they were not the true Muslims for me. They were different from my friends, being at a Catholic school and university," Chaftari said.
"The true Muslims were the ones I heard about. They were lazy, dirty and would never reach university. They were somehow not meant to live the way we were living because they were Muslims. I was the inheritor of the Phoenicians and French, while they were Arabs and Muslims, and I was a child of a better god," he said.
Chaftari's entry into his country's civil war happened gradually as he began hearing news of a series of political and security developments that appeared to threaten Lebanon's Christian community. In 1969 Lebanon signed an agreement with the Palestinians giving them the right to have their own army units and use Lebanon as a base for attacks against Israel. In 1973, heavy clashes broke out between the Lebanese army and the Palestinians.
With the advent of the war, Chaftari, at age 20, bought his first gun -- a Kalashnikov -- at a Palestinian refugee camp on the outskirts of Beirut. "In 1975 when the incidents started, I was ready," he said.
He moved through the ranks of the Christian militia of Kataeb as a telecommunication specialist.
"The task was to protect the Christians, detect any spies in the Christian areas and in our ranks. It was about interrogating those who were arrested, spying on the enemies, demolishing their headquarters, and trying to murder their leadership. This was our task. And I did it all. Until I had a lot of blood on my hands," recalled Chaftari, recounting his role in the civil war that ended in 1990.
"The first one you might feel something, the second one less, the fourth becomes a number. When you kill a person you kill a part of yourself. I thought I never killed innocents. I killed those I felt were using violence against Lebanon. I was living a feeling of innocence in the war. Why would I confess a sin if I was protecting Christ, Christianity or Lebanon?" he said, explaining his thinking at the time.
In 1986, after differences with his own unit, he fled to the Bekaa Valley town of Zahle.
There, he met Initiatives of Change, a global nongovernmental organization dedicated to "building trust across the world's divides." It was led in Zahle by a Maronite bishop. Even before the war ended efforts were underway to find common ground between warring factions.
"If you're ready to change the world, are you ready to change yourself first?" Chaftari remembered the bishop asking him.
"Little by little I started looking into this mirror that showed me I had become a monster," he said. Chaftari admitted the most difficult part was acknowledging that he had killed in the name of Christianity.
To his surprise, he met Muslims who had similar prejudices against Christians.
"The Muslims almost had a parallel, concordant past. Why they became soldiers, how thought they had to get rid of us," he said. "This is where I learned to listen to Muslims."
Chaftari soon realized he had a much larger task, far beyond these intimate dialogue sessions. One day, he heard his son joking with a friend and making a bad remark about Muslims. That's when Chaftari decided to publicly apologize for his role in the civil war. In 2000, he wrote an open letter of apology.
"Since then, I think I've put myself in God's hands," he said.
These days, Chaftari dedicates much of his time engaging with Lebanon's youth through Fighters for Peace, a group of about 25 former civil war fighters who over the last three years have spoken with more than 7,000 students, produced documentaries and theatrical productions telling their stories, and run a conflict resolution summer camp.
"Our target is mainly the youth, 14 to 15 years old. We believe this is the age they're ready to be violent. Most of us were children when we first carried a gun," said Ziad Saab, a member of the group who fought with a communist militia during the civil war. The ex-fighters started meeting in 2012, when there were regular clashes in Lebanon's northern city of Tripoli, evoking fears of the start of a larger conflict.
"After the war was finished in (the) 1990s, many of the ex-fighters didn't manage to adapt to society. There was no real reconciliation," Saab said.
He said he hopes more former fighters will join the effort, although he understands the difficulty of opening old wounds and admitting wrongdoing.
Carol Hakim, a researcher on Lebanese nationalism, says that Chaftari's story is not unusual. Many young people enter wars as activists for their own causes, and by the end lose sight of why they started in the first place. What is unusual about his story, she said, is his openness to reconciliation with previous foes.
"I really believe there's a price to pay for peace," Chaftari said. "The first price I paid was standing in front of the Lebanese. I did what I did, standing almost nude. Whatever price to pay to avoid new civil wars, I'm ready to pay. This is what I've been doing since then."