Digital media has made it easier than ever for malicious actors to distribute fake news, including video, but at the same time, it has also made it easier for journalists to debunk or verify that news using tools like Google Earth. The BBC’s Africa bureau provided a real-life lesson in how to do just that in a Twitter thread on Monday, about a video that started to circulate on social media in July of this year. The clip appeared to show two women and two children being blindfolded and then shot multiple times, and the shooting appeared to have been committed by soldiers in Cameroon (A warning: Although the most gruesome part of the video has been edited out, it may still be disturbing for some viewers.)

THREAD In July 2018, a horrifying video began to circulate on social media. 2 women & 2 young children are led away by a group of soldiers. They are blindfolded, forced to the ground, and shot 22 times. #BBCAfricaEye investigated this atrocity. This is what we found… pic.twitter.com/oFEYnTLT6z — BBC News Africa (@BBCAfrica) September 24, 2018

The government in Cameroon initially dismissed the video as “fake news,” and claimed that the guns used by the men in the video were not like the ones the Cameroon army carries, and also that the camouflage clothing they were wearing wasn’t the same as that used by the Cameroonian military. The minister of communication said that the video was “nothing but an unfortunate attempt to distort actual facts and intoxicate the public,” and that its “sincerity can be easily questioned.” The BBC set out to verify whether the shooting was real, and whether it took place where and when it was said to have happened.

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The reporters started with the mountain range that can be seen in the background of the video. A source in Cameroon told the BBC team the ridge looked similar to one in the northern part of the country, and using Google Earth footage of that area they were able to confirm that it matched the location—a town close to the Nigerian border, where Cameroonian soldiers have been fighting the jihadist group Boko Haram. The BBC reporters also matched trees, roads, and buildings in the area to those appearing on Google Earth. And they were also able to pinpoint the time: A building in the video has walls, but the same building on Google Earth has no walls until November of 2014, meaning the shootings must have taken place after that.

When did this happen? Again, the video contains clues. This building is visible in the video. But satellite imagery reveals that, back in November 2014, the walls around it had not yet been built. The killing happened after November 2014. pic.twitter.com/XODYqL5LRY — BBC News Africa (@BBCAfrica) September 24, 2018

Another building in the area that was demolished after February of 2016 allowed the team to further pinpoint the time range, and looked at the shadows cast by the soldiers allowed them to narrow it ever further, to between March 20 and April 5, 2015. The BBC team also managed to confirm that—contrary to the Cameroonian government’s denials—the weapons used in the video (Serbian-made Zastava M21 rifles) are used by some of the Cameroonian army, and images posted to Facebook of soldiers in the region showed that they do in fact wear the kind of camouflage pattern that the killers in the video do.

After weeks of denying that the video showed members of the Cameroonian army, the government changed its tune in August and announced that seven members of the military had been arrested and were under investigation for the killings. Although the BBC investigation didn’t cause the government to change its mind, the fact that it was able to prove that specific soldiers were involved, in such a comprehensive and detailed way, is an inspiring use of digital journalism, and could help convict them.

The BBC is far from alone in doing this kind of digital forensic work. Amnesty International also did some early research into the Cameroon video. One of the pioneers of this particular digital research, British investigative journalist Eliot Higgins, got his start analyzing YouTube videos of the Syrian war in 2012, in his spare time, studying serial numbers and measuring the size of exploded bombs. Higgins eventually became a recognized expert in Syrian warfare, cited by New York Times war reporter C.J. Chivers among others, and was able to prove that the Syrian government had shelled its own citizens with “barrel bombs,” something Human Rights Watch has argued should be considered a war crime.

Higgins now runs a journalism project called Bellingcat, which has used social media and digital forensics to show that Russian government agents likely shot down a Malaysian passenger jet in Ukraine with a surface-to-air missile. At least one journalist and researcher who works with Bellingcat also helped BBC’s Africa bureau with their research into the Cameroon killings.

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Mathew Ingram is CJR’s chief digital writer. Previously, he was a senior writer with Fortune magazine. He has written about the intersection between media and technology since the earliest days of the commercial internet. His writing has been published in the Washington Post and the Financial Times as well as by Reuters and Bloomberg.