He cries for help and they mock him in Russian, drowning his agonized screams out with laughter. The background of the video, which was uploaded to the internet, plays a Russian nationalist military song, “I Am Russian Special Forces.” Mohamad, a 31 year-old Syrian construction worker who was father to four young children, is the victim of this horrifying amateur video. He disappeared while returning from a job in Lebanon in March 2017. Mohamad’s last words were those of Shahada, a declaration about his Muslim faith. He was 31-year-old Syrian construction worker and father of four young children. He disappeared in March 2017 while returning from a job in neighboring Lebanon. The graffiti read “for VDV, reconnaissance,” a reference the Russian airborne forces. Read MoreThe independent investigative Russian newspaper Novaya Gazeta has identified at least one of the men in this video as a mercenary with the shadowy Wagner group — a private military organization that has links to Yevgeny Privgozhin. The Kremlin denies any connection to Wagner and insists that Russian private military companies are illegal. Prigozhin previously denied any connection to Wagner. Despite multiple attempts to reach him for comment, he and his companies have not spoken to CNN in recent times. “These people risked their lives and by and large, this is also a contribution to fighting terrorism… but this isn’t the Russian state, nor the Russian army,” stated President Vladimir Putin in 2019. CNN special report: Since 2015, Putin’s private army Russian forces has been operating in Syria. There is substantial evidence to support the claim that Wagner’s presence there is linked to Russian military deployment. Analysts believe it is impossible that Wagner could exist without Putin’s approval. It is true that the training camp it runs in southern Russia is attached at a Russian special forces base. In fact, the three NGOs from Russia, France, and Syria filed a landmark legal case against Wagner. They alleged that the group was involved in the atrocity and the possible war crimes committed by the men in the video. Mohamad’s brother Abdullah filed the lawsuit in March. This is the first time that anyone has attempted to hold Wagner’s brother Abdullah accountable for the atrocities they have committed. Rights groups claim that this has allowed Moscow to expand its global footprint, which has allowed Moscow to pursue a foreign policy in places such as Syria, Ukraine, Libya and Sudan. Abdullah, a Syrian refugee, has never spoken publicly about his brother’s death. In an exclusive interview with CNN, he said that he broke his silence to bring attention to the tragedy that afflicted his family. Abdullah requested that CNN hide his identity and the location of the interview to protect his family members who still live in regime-controlled Syria. Abdullah stated, “My brother has died and he will never return.” “I want the whole world to know about my brother’s case so that these criminals can be held accountable.” Last phone call to family. Mohamad told Abdullah in April 2017 that he was being held by the regime as he crossed into Syria. He had worked in Lebanon for eight months. He claimed he was taken to Damascus, and forced to join military service. However, he said that he intended to flee. Mohamad called Mohamad ten days later to inform him that he was going to Homs the following day and that he would be escaping at night. It was his last phone call to his family. Abdullah said that he had spoken to his father and mother to ask for forgiveness. He added, “Give your best, I am going do something, I am leaving, I don’t know if I can get back to you or no.” We tell Syria’s human stories to make sure the ‘victors” don’t write its history. Abdullah said that his brother had asked him “to take care of my wife,” and added: “I am entrusting your with my family.” Abdullah explained, “It was that type of talk, it seemed as if he knew what was coming to him.” Mohamad never had the opportunity to meet his youngest daughter. With the civil war in Syria raging and their remote village lacking internet and phone connectivity, it was difficult for Mohamad’s loved ones to discover what had happened. His family only discovered the horror of his torture when a video clip showing it online several months later. “One day, a man from our town sent me the video clip. He said that it could be his brother. Abdullah, his voice strained, said that he recognized my brother from his clothes, voice, and appearance. “He was being tortured, they weren’t Syrian, we didn’t understand what they were saying. Abdullah shared the video with other family members, but did so out of fear for his elderly parents. He said, “When I first saw that video, I still had hope that he was still living.” He was being tortured but he was still alive and moving. We hoped he was still alive, and that he was in a hospital. Their father went to Damascus to search for his son in hospitals and prisons in the capital of Syria. “About two more months later, the second footage emerged, that’s when we believed our brother had died,” the 27-year old, now visibly distraught, said CNN. “When I saw the second video, which showed Mohamad being executed], I stayed in a hotel room. I stayed in the same room for three days. He was more than my older brother. He was also my friend. Abdullah stated that we were always together. “My brother (the other) developed a kind of psychological illness from the videos. “Landmark legal caseWagner forces have been used in Syria as the tip of a spear, but their shadowy presence affords Moscow an opportunity to deny that it was involved. However, when the bodies of Russian mercenaries began to return home, it became obvious that it was a Wagner operation. Moscow refuses to talk about the oil field destruction. CNN spoke to a source who was connected to Wagner and had visited the wounded fighters on their return to Moscow. In the days that followed the attack, a Russian media outlet visited the mother of a Syrian fighter and confirmed that her son was not a Russian regular soldier. CNN obtained a copy from Evro Polis and Syria’s government in February 2018. Evro Polis is entitled to 25% of the oil field revenue if they are seized from rebel territory. Evro Polis gets 25% of the revenue from oil fields if they are seized from rebel territory. CNN and other researchers have tracked the frequency of flights from Latakia to other theatres in the region. CNN obtained a document that details the agreement between Yevgeny Prgozhin and a Russian 223rd Flight Detachment to use their aircrafts. “It was our children that they killed” A CNN investigation in June revealed evidence that Russian mercenaries were perpetrating war crimes and human rights abuses within the Central African Republic (CAR). According to witnesses and community leaders, the Russian government denied the allegations and said that the contractors in CAR were not armed and did not participate in hostilities. The CAR government also denied these allegations, but stated that an inquiry would be conducted to establish the facts. This coincided with the 10th anniversary of Syrian uprising. The advocacy groups stated that the complaint “…is an unprecedented attempt to fill in the impunity gap, and bring Russian suspects accountable.” “Syrian activists, victims of atrocities committed by all parties in the conflict in Syria have been working tirelessly from 2011 to get accountability,” they stated. They also said that there are only limited avenues for victims’ families and justice to be obtained. The International Criminal Court does not have jurisdiction in Syria as the country is not a signatory of the Rome Statute. This leaves many victims of the conflict without any recourse. Russian vets attempt to bring the Kremlin’s mercenaries into the cold. Syrians are increasingly turning towards European courts, especially France and Germany, in their quest for justice. It gives a national court jurisdiction over grave offenses against international law, even if they are not committed on Syria’s territory. This was the first trial of anyone linked to the regime in Damascus. Another case is pending. Clemence Bectarte (a lawyer at FIDH) said that they chose to file the case in Russia because of “the unique opportunity due to the strong legal basis in Russia to claim jurisdiction… this court is the natural one for this case.” “We are referring to Russian perpetrators, people that could be arrested in Russia if the political and judicial will to push the case forward. Bectarte said that universal jurisdiction should always be considered as a last resort. Abdullah has never heard about Wagner. He said he only wants to see his brother’s executioners held responsible. He said, “If someone had not given them the green signal, they wouldn’t do something like that.” “We won’t be like them and demand that [what happened to my brother] also happen to them, but the least they should get is jail.” Abdullah claims that his brother’s suicide has put him in a difficult position. He must care for Mohamad and his children, as well as deal with the trauma from the videos. It has also led him to a dangerous and long search for justice against an invisible enemy. He believes it is worth taking the risk. He said, “I’m not worried about me.” “I just want them held accountable, even though it may cost me my life.” This report was contributed by Eyad Kourdi, CNN.