The footage is at odds with almost every account Sarfo, 28, has given of his time in Syria, including his statements to German authorities that he merely "stood on the side" while the shooting took place and adamantly "said no to the killing."
The video serves as an alarming example of how little European security services know about hundreds of militants returning to the continent after fighting in Syria - often with the Islamic State.
European security services face worrisome blind spots about more than 6,000 militants who left to fight in Syria over the past five years, a flow that has begun to reverse now that the Islamic State is losing territory. Despite his trip to Syria, Sarfo was able to board a return flight from Turkey last year and was arrested upon arrival in Germany.
The new evidence will "probably lead to a new investigation and case" against Sarfo, a senior German security official said. "The difficulty for authorities and the justice system is that we don't have any independent source on the ground in Syria to describe whether what Sarfo or others like him have told us is indeed accurate."
"We can see the videos, yes," the official said, referring to the large volume of propaganda put out by the Islamic State. "But what has happened before or after that, we don't know." The official, like others, spoke on the condition of anonymity, citing the sensitivity of the case.
Sarfo's attorney, Udo Würtz, seemed stunned when shown the new video of his client. "I can't say anything about this - this is surprising to me," he said. Moments later, he said that the images show that Sarfo was doing "more than just standing around, yes, but I am not sure it will change his sentence."
Würtz met with Sarfo on Tuesday at the prison in Bremen and showed his client a printed image from the video in which Sarfo is aiming his gun at the hostages in the video. Würtz said he was not authorized to comment on their exchange.
Sentencing documents indicate that authorities not only accepted Sarfo's sanitized version of events but credited him for being forthright, concluding that he had "credibly distanced himself from the terror organization" once in custody by being willing to incriminate others.
Germany has been spared the devastation of terrorist attacks like those in Paris and Brussels, but the country remains a priority target for the Islamic State. At least 870 German citizens or residents have traveled to Syria and Iraq, officials said, and authorities estimate that one-third of those have returned.
Security agencies across Europe face a stream of "individuals who have battlefield experience in numbers that we have never seen before," said Lorenzo Vidino, an expert on Islamist militancy at George Washington University. "There are cases where authorities have a good grasp of what the individual did. But in many cases, authorities simply know that an individual espouses jihadist ideology and went to Syria but possess no information on what he did while there."
A complete account of Sarfo's involvement with the Islamic State eluded German authorities even though he made little effort to conceal his association with the terrorist group and appeared in one of its propaganda videos.
That recording shows two Islamic State operatives executing hostages who were forced to kneel among the columns in the ancient Syrian city of Palmyra, which came under Islamic State control last year. Sarfo appears only briefly in that video, striding across the screen in combat fatigues with the group's iconic black flag.
But the Islamic State camera crew in Palmyra captured other video in the city that was left out of the propaganda release. Portions of this additional footage were provided to The Washington Post by an individual inside the Islamic State, which is eager to discredit Sarfo because of his repeated denunciations of the group.
In an April interview with the British newspaper the Independent, Sarfo said that he had "witnessed stonings, beheadings, shootings, hands chopped off and many other things." The Islamic State, also referred to as ISIS or ISIL, is "not just un-Islamic, it is inhuman," he said.
A German native of Ghanaian descent, Sarfo was in Syria for only a three-month stretch in 2015 before he fled and was arrested after returning to the German city of Bremen, his home town. But he has drawn extraordinary attention from authorities and news organizations because of his willingness to talk about the Islamic State's efforts to use recruits from Europe in plots against their home countries.
The FBI has sought permission to question Sarfo, as have authorities from Austria and other countries, German officials said. The FBI declined to comment.
Sarfo was initially uncooperative with the police after his arrest in July of last year, German officials said. He changed his stance, however, after the Islamic State released the Palmyra propaganda video in August, confirming his association with the group.
Sarfo then submitted to lengthy interrogations, transcripts of which were obtained by The Post, telling investigators that he was approached upon his arrival in Syria by members of Amniyat, an entity within the Islamic State responsible for internal security and external plots. Sarfo said he refused requests to take part in attacks in Europe and was instead assigned to an elite fighting group. He also spent hours going over photos from Syria, helping investigators to identify other Western militants.
"He not only passed on concrete details of events," the sentencing document said, "but also provided details as to the structure of the organization, people trafficking routes."
His claim to have been a bystander to the killings in Palmyra and other violence went largely unchallenged by German investigators. In subsequent interviews with at least half a dozen media organization, he depicted his supposed refusals in more dramatic fashion.
Speaking on-camera with German broadcaster ZDF this year, Sarfo said that he and other fighters were driven to Palmyra, taken into a room and asked to take part in the execution of seven men whom he described as civilians being forced to wear Syrian army uniforms for a propaganda film.
"I refused. I did not raise my hand," Sarfo told ZDF, which worked with The Post in the reporting of this article. Even when pressured by more senior Islamic State operatives, Sarfo said, he stood firm: "I don't know this person. He didn't do me any harm. I won't kill him."
The new video depicts Sarfo in a less defiant light. He is shown helping to position panicked hostages in the center of a crowded street just before they are shot. Another Islamic State militant, identified in German records as an Austrian, Mohamed Mahmoud, is among the first to open fire. Amid the shooting, Sarfo appears to shout "Allahu akbar" from an adjacent sidewalk.
As bullets rip through the victims' bodies, Sarfo cocks a pistol and aims at one of the fallen figures. The camera's view is obscured by another militant before any muzzle flash can be seen. But a body on the street spasms with impact before Sarfo returns his gun to its holster.
Sarfo "was not shy about helping with preparing for executions and was actually eager to participate," said the individual inside the Islamic State who provided the video. The individual disputed some of Sarfo's claims, saying he was never made a member of an elite fighting group or in position to gain sensitive information about Amniyat. "The only encounter he had with security people was when they began to question him about his motives and why he came," the individual said.
German officials acknowledged they had not seen the more incriminating video when Sarfo was convicted of membership in a terrorist group and violation of German gun laws. Though given a three-year sentence, he is eligible to be released in two.
"A defendant in terrorism cases like Sarfo will always try to play down his own role," the German security official said. "We did take this into account when we questioned him, but at the end of the day what counts is the evidence we have against this person."
Sarfo "always claimed that he did not participate in any killings or executions," the official said. Because of the disparity between his accounts and the video, the official said, other information Sarfo provided to authorities and journalists "will have to be questioned and no longer be considered trustworthy."
Of the approximately 290 Germans who have returned to that country from Syria and Iraq, the government has identified at least 70 who participated in the fighting. Many of the others probably did so as well, but the government has no proof, officials said.
European countries have tightened their counterterrorism laws in response to the flow of foreign fighters to and from Syria. But the new statutes are generally far milder than those in the United States, where the catchall "material support to terrorism" law updated after the Sept. 11, 2001, attacks can carry a 15-year sentence for each count.
Sentences for terrorism-related convictions in Europe range "from a few months to a handful of years," Vidino said. Most impose five- to eight-year sentences for membership in a terrorist group, but the actual time served is often significantly less. In one of the more extreme cases, a Swiss national who fought with the Islamic State in 2014 was sentenced to 600 hours of community service.
"The penalties are low and the evidence is very difficult to produce," Vidino said. As a result, he said, European services face a multilayered challenge of screening refugees from Syria, tracking returning fighters and monitoring convicted terrorists after their release.
There are other troubling aspects of the Sarfo case, including his ability to board a flight from Turkey to Germany on July 20, 2015. Court documents indicate that after fleeing Syria he went to the German consulate office in Izmir, Turkey, to report that his passport had been lost.
In fact, Sarfo's passport had been confiscated by German authorities months earlier in an effort to block his efforts to get to Syria. German records, which were obtained by The Post, show that he was detained by Turkish security forces in 2014 and returned to Germany after an earlier, unsuccessful attempt.
Sarfo tried again in 2015, this time using a relative's passport and driving with another German militant through Bulgaria into Turkey before finally reaching the Islamic State. In early July, German authorities notified their Turkish counterparts that they suspected Sarfo was in Turkey and had applied for a temporary passport using the name Kevin Behns.
Three weeks later, the Germans sent another notice to Turkey, saying that the individual claiming to be Behns had purchased an airline ticket to fly to Bremen. German officials blamed Turkey for the lapse in letting Sarfo aboard the Bremen-bound flight.
Germany asked for additional screening of the passenger they suspected to be Sarfo, but made no effort to prevent him from boarding the flight or to ensure that security officials were onboard, a senior security official in Turkey said.
Germany issued an arrest warrant for Sarfo that enabled authorities to detain him, the German security official said. But that didn't happen until the flight had departed.
