Drone strikes conducted by the United States during a 5-month-long campaign in Afghanistan caused the deaths of unintended targets nearly nine out of ten times, leaked intelligence documents suggest.

The apparent 10 percent success rate with regards to a specific span in America’s drone war is among the most damning revelations to surface so far as the result of a series of articles published by The Intercept on Thursday this week which rely on classified and confidential intelligence documents supplied by an unknown source.

“These docs illustrate what a video game, drained of all humanity, these drone assassinations have become,” founding editor Glenn Greenwald tweeted on Thursday.

Edward Snowden, the former National Security Agency contractor now in exile, has previously supplied journalists at the online news site with top-secret documents detailing the intelligence community’s eavesdropping efforts — the likes of which has sparked international debates concerning privacy and civil liberties implications, among other factor, as well as calls for legislative reform in the U.S. and abroad.

But the latest trove of documents — previously unpublished reports concerning suspected terrorists, signals intelligence gathering and, ultimately, the launching of often lethal drone strikes — are the apparent offerings of a new source likely to soon be scorned by the U.S. government as well.

“This outrageous explosion of watchlisting — of monitoring people and racking and stacking them on lists, assigning them numbers, assigning them ‘baseball cards,’ assigning them death sentences without notice, on a worldwide battlefield – it was, from the very first instance, wrong,” the unnamed source told The Intercept.

Ryan Devereaux, a journalist with the website, reported that “During one five-month period of the operation, according to the documents, nearly 90 percent of the people killed in airstrikes were not the intended targets.” Nevertheless, the U.S. government considers many of these casualties to be enemy combatants, according to the the source, despite the strikes more often than not ending in the deaths of women, children and other civilians who become collateral damage of targeted attacks and are subsequently written off as adversaries killed during war, regardless of status.

“In Yemen and Somalia, where the U.S. has far more limited intelligence capabilities to confirm the people killed are the intended targets, the equivalent ratios may well be much worse,” Mr. Devereaux wrote.

Hina Shamsi, director of the ACLU National Security Project, condemned the revelations: “The Obama administration’s lethal program desperately needs transparency and accountability because it is undermining the right to life and national security.”

“These eye-opening disclosures make a mockery of U.S. government claims that its lethal force operations are based on reliable intelligence and limited to lawful targets. In fact, the government often claims successes that are really tragic losses,” Ms. Shamsi added.