It's been just over two years since Edward Snowden leaked a massive trove of NSA documents, and more than five since Chelsea Manning gave WikiLeaks a megacache of military and diplomatic secrets. Now there appears to be a new source on that scale of classified leaks—this time with a focus on drones.

On Thursday the Intercept published a groundbreaking new collection of documents related to America's use of unmanned aerial vehicles to kill foreign targets in countries ranging from Afghanistan to Yemen. The revelations about the CIA and Joint Special Operations Command actions include primary source evidence that as many as 90 percent of US drone killings in one five month period weren't the intended target, that a former British citizen was killed in a drone strike despite repeated opportunities to capture him instead, and details of the grisly process by which the American government chooses who will die, down to the "baseball cards" of profile information created for individual targets, and the chain of authorization that goes up directly to the president.1

All of this new information, according to the Intercept, appears to have come from a single anonymous whistleblower. A spokesperson for the investigative news site declined to comment on that source. But unlike the leaks of Snowden or Manning, the spilled classified materials are accompanied by statements about the whistleblower's motivation in his or her own words.

"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 source tells the Intercept. "We’re allowing this to happen. And by ‘we,’ I mean every American citizen who has access to this information now, but continues to do nothing about it."

Reports first surfaced in the fall of last year that the Intercept, a news site created in part to analyze and publish the remaining cache of Snowden NSA documents, had found a second source of highly classified information. The final scene of the film "Citizenfour," directed by Intercept co-founder Laura Poitras, shows fellow Intercept co-founder Glenn Greenwald meeting with Snowden in Moscow to tell him about a new source with information about the U.S. drone program, whom he says has been communicating with the Intercept's Jeremy Scahill. At one point, Greenwald draws Snowden a diagram of the authorization chain for drone strikes that ends with the president, one that looks very similar to the one included in Thursday's publication.

"It's really risky," Snowden tells Greenwald in the scene. "That person is incredibly bold."

"The boldness of it is shocking," Greenwald responds, "But it was obviously motivated by what you did."

In the scene, Greenwald also tells Snowden the security tools the Intercept is using to communicate with the source, writing the names of the software on a piece of paper in what may have been an attempt to avoid eavesdroppers. Those security tools, along with the Intercept's reputation for combative, unapologetic investigation of the U.S. government, may help explain how the site seems to have found another Snowden-like source of national security secrets. The Intercept and its parent company First Look Media employ world-class security staff like former Googler Morgan Marquis-Boire, Tor developer Erinn Clark, and former EFF technologist Micah Lee. Far more than most news sites, its reporters use tools like the encryption software PGP and the anonymous upload system SecureDrop to protect the identities of its sources.

Whether those measures can actually protect this particular source—or whether the source Greenwald told Snowden about is even the same one who leaked the Intercept's Drone Papers—remains to be seen. Yahoo News reported last year that the FBI had identified a "second leaker" to the Intercept and searched his or her home as part of a criminal investigation.

If that reported search of the leaker's home did happen, however, it doesn't seem to have slowed down the Intercept or its whistleblower. A year later, no arrests or charges have been made public, and the site has now published what appear to be the biggest revelations yet from its new source.

In the Citizenfour scene, Snowden tells Greenwald he hopes that the new leaks could help change the perception of whistleblowers in general. "This could raise the political situation with whistleblowing to a whole new level, he says.

"Exactly," Greenwald responds. "People are going to see what’s being hidden by a totally different part of the government."

Read the Intercept's full Drone Papers release here.

1Correction 10/15/2015 12:45pm: An earlier version of this story stated that a former US citizen, Bilal el-Berjawi, was killed by a drone. In fact, el-Berjawi was a former British citizen.

2Updated 10/15/2015 2:15pm to include Erinn Clark in the list of First Look Media security engineers.