But some less obvious clues, along with a bit of mathematical know-how, allowed the journalists to narrow down the time of the murders to an astonishing degree. A glimpse of a dirt footpath in the footage told them that it must have been captured in Cameroon's hot, dry season – between January and April. And then, by using the soldiers in the video as makeshift human sundials, they were able to pinpoint the killings to just a two-week window.
The only question left was who the soldiers in the video were. Amnesty's investigators had already pointed out that their uniforms and insignias strongly suggested they were Cameroonian, but the BBC's journalists actually managed to identify one of the individuals in the video – and they did it using one of the best, most detailed databases on the planet: Facebook.
Thanks to their Facebook-surfing, they were also able to debunk the "fake news" claims. For instance, although the government said soldiers in that area would not wear the "forest" uniforms shown in the footage, the BBC found photos showing just that: Cameroonian soldiers in uniforms matching those in the video, and tagged to the exact location determined by the journalists.
In August, a month after the video originally surfaced online, Cameroon's Minister of Communication released a statement saying that seven members of the military had been disarmed, arrested, and imprisoned while under investigation. Three of the soldiers on the list could be matched to the footage thanks to the work by the BBC.