After Apple refused to crack its own encryption in order to help unlock the iPhone that belonged to the San Bernardino shooter, FBI managed to hack into the device. A new and heavily redacted 100-page document from the FBI provides some context as to how the bureau was able to do so.

According to the documents, the FBI hired a third-party source to help break into the phone of Syed Rizwan Farook, who along with his wife killed 14 people at a holiday gathering in San Bernardino, Calif. in December 2015.

However the bureau kept censored some of the most pertinent information, including who it contracted to complete the work and how much it paid. Those details were marked as “secret” before being turned over.

The documents do reveal the FBI signed a non-disclosure agreement with the contractor it hired for the job. The FBI didn’t seek multiple bids from providers who may be able to complete the task, citing a potential risk to national security were it to widely disclose its needs.

The FBI was approached with inquiries from three different companies interested in helping to unlock the device, but were unable to provide a surefire way to unlock the phone in a timely enough fashion for the FBI, it said.

The records were revealed thanks to a federal lawsuit filed against the FBI by the Associated Press, Vice Media and Gannett. The media organizations filed suit against the bureau after it declined to provide information under a Freedom of Information Act request.

The original requests followed a surprise announcement in March 2016 from the Department of Justice that it had successfully gained access to the iPhone 5C that had belonged to the San Bernardino shooter. The FBI was previously unable to access it, and risked wiping the device if it incorrectly attempted to breach the device’s security.

It was believed at the time only Apple was able to unlock the device. The process would have required the company to undermine its own security protocols, potentially opening up a threat for all its users by proving its encryption could be cracked. Apple refused to unlock the device despite considerable pressure from the Department of Justice.

The FBI declined to provide any information as to how its contractor was able to bypass the security measures and access the device.