"It is not enough to say I am sorry, you should do something about it", says Assad Shaftari. This public servant, as he describes himself, had a long rocky path to walk to become the preacher of peace and reconciliation he is today. Once a young twenty-year-old engineering student on the eve of Lebanon’s civil war in 1975, he joined a telecommunications unit in a Christian armed group and later took an artillery course.

Raised in a Christian school and studying later at a Christian university, he had many stereotyped concepts about fellow Muslim citizens. Many Christian leaders at the time believed Muslims were second class citizens. He has also learned to hate the Palestinians, armed Muslims who had made Lebanon their headquarters.

"I was a wrong believer, a bad believer", Shaftari tells me. He was led to believe, and he did believe, that by fighting Muslims and Palestinians, he was defending his community, the country, the Pope, Christ, the cause. "What cause?", he asks himself. It was all wrong.

But back then it all sounded right. He kept going to the Sunday Mass. He had his conscience clear. In his words, he did not kill civilians but armed men, whether Palestinians or people involved in attacks in Christians areas. He did not steal or loot, he believed what he got himself involved in was a simple act of self-defense. And as the war got bigger, so did he. He became second in command of the Intelligence Unit in his group.

He says he acted "like a small god". It was up to him to rule over the fate of captives, whether killed or exchanged for others or used to bridge intelligence gaps. He said: "I was not conscious of what I was doing, I was just keeping score… I had lost my sense of humanity".

When I asked him a question that sure is a cliché, "do you how many persons you have killed", he quoted a verse in the Koran, that the killing of one person is equivalent to the killing of mankind. Yes he did quote the Muslim holy book, and he admits that if he had known more about Islam in his youth, he wouldn't have become the religious fanatic he was.

What was his wake up call? In 1988 his wife attended a meeting with the Initiatives for Change movement. She was excited about it, but he was skeptical and kept looking for a hidden agenda. He was invited to a meeting and got introduced to the four absolutes one should build inside. Honesty, purity, unselfishness and love. He thought he had them all. Little by little, he started wondering, was he really on the side of God? Only then he realized he had a bloody path and past.

What came next was not easy. He tells me, "imagine introducing light into a dark room, you thought it was clean but you discover it was full of dirt". Shaftari had to clean his room, his life. "The biggest Jihad (struggle) is with oneself", once more I listen to him echoing a famous Islamic principle.

He was ridiculed and received death threats. His former fellow fighters doubted his intentions. He says they only believed him when he published his famous apology letter in 2000. He acknowledged he wasn't practicing the "true Christianity which is about loving others". But even then, he was told, "why go first, couldn't you have waited for Muslims to come forward?"

He later decided to address the victims privately. "Many people didn't know I was behind their sufferings. I can't take many out of my mind. I had to take responsibility for my wrongs to be able to redeem myself. I visited a lot of my victims' families". He pauses so I ask about their reaction. "There was pain and bitterness, but many forgave me. They were in pain, and so was I".  He joined efforts with some of them to reveal the fate of their relatives, the "disappeared".

Other countries, mainly in Africa, have held truth commissions and encouraged former combatants to step forward with any information they might have about other fighters and civilian victims. This wasn't the case in Lebanon. The war was officially over with the Taef agreement and legal amnesty was granted. Shaftari points that the law didn't specify that amnesty was not to be repeated, and it didn't put the fighters in a rehab process through community service. Ironically, many warlords became acclaimed politicians, members of parliament and consecutive governments. Some were Shaftari's allies.

He insists he has no political aspirations but works to prevent new wars. "We are living in a hidden civil war, it has been the case since 2005", when former Prime Minister Rafik Hariri was assassinated. Cold hostilities occasionally flare up into violence, only now it is between Muslims themselves, Sunnis and Shiites, or Sunnis and Alawites. It happened in Beirut in May 2008 and in Tripoli, Northern Lebanon, over and over in the last few years.

Wherever he goes in Lebanon, he sees angry young men. "I can almost visualize their death, their becoming a picture on a wall", he says. In Nabatiye, a stronghold of Hizbullah in Southern Lebanon, he recently listened to students wanting to fight fellow Lebanese supporting the "Islamic State" (IS) terrorist group. Shaftari told them quietly they should consider another approach, to cut what they call "the others" links to IS, to find them decent jobs and try to understand the roots of their fundamentalism. He argued it was totally unacceptable for a Lebanese to hold arms against a fellow citizen, "a brother", in his words.

He tells me the director of the school spoke as aggressively as the students. It worries him to witness the fears the Shiite youth have nowadays, to see "a Lebanese sect getting afraid after long being feared".

A Christian audience would show distrust to Muslims, whether Sunnis or Shiites. Young Christians want to get armed to protect their neighborhoods from Muslims and Syrian refugees. It rings a bell. So Shaftari would simply recite the story of his life and add his new conviction. In face of religious fundamentalism, only moderate Muslims would defend Christians.

In Tripoli which he visited several times last year, his work was much harder, "because they live in an actual war".  It was dangerous for Alawite young men to get to the city from its sidelines, yet there was still hope, they were unarmed. This approach does not work though with those who fight, they are similar to his old comrades. All need psychological decontamination, to be cleansed from the burden of violence. This is a cause very dear to Shaftari's heart and he works for it with 12 volunteers through a newly established organization, Fighters for Peace.

To me and almost everyone who interviewed him over the years, Assaad Shaftari is a sincere repentant. It shows in his eyes and words. He admits he still struggles with himself in search for inner peace, "I do need to remind myself of who I am now so my old version never comes back".

I ask him if he would hold arms again, he answers firmly, "never, not even to defend myself". I keep asking, what if the Lebanese army facing IS and the Syrian Jabhet An-Nousra calls all capable men to volunteer in defending the country. "There are other means for me to answer that call. I will not be armed again".

Shaftari defines himself as "a human being first, then a Christian respecting other religions". He believes Jesus "didn't come to earth to establish a Christian state or a Christian society but to touch the hearts of humans. So it does not really matter if the Christians' presence diminishes in Syria, Iraq, Palestine or Lebanon. Christianity is about hearts not lands". Who would have thought this comes from a once religious fanatic who took himself for a crusader?