In a court filing, the Justice Department said it had accessed the "data stored on Farook's iPhone and therefore no longer requires the assistance from Apple," though it did not specify how it gained this access.
Apple welcomed the news. "This case should never have been brought," Apple said in a statement.
"This case raised issues which deserve a national conversation about our civil liberties, and our collective security and privacy," it added. "Apple remains committed to participating in that discussion."
The developments lend some credence to the theories that this was never about gaining access to a single device, but instead about strong-arming Apple into providing a brute-forcing tool to the FBI, capable of quickly cracking any Apple device.
Earlier this month, it was reported that Apple plans to put cloud encryption keys in the hands of its users.
Currently Apple looks after these keys, and so if served with a warrant, it must hand over iCloud access to authorities. By passing on password-protected keys to users, Apple would bolster the physical encryption found on its devices, with access available solely through customers rather than Apple, even if the company wanted to.
Updated 9 March 2016: Edward Snowden has outright dismissed the FBI's claims that only Apple has the technology to unlock the iPhone in question.
Updated 4 March 2016: Now the UN's high commissioner for human rights, Zeid Ra'ad Al Hussein, has weighed in - urging the FBI to proceed with caution.
Apple is embroiled in a battle over privacy with the FBI that could have wide-reaching repercussions, and now major figures in the technology industry have been pulled into the debate.
The FBI is demanding Apple creates a custom operating system that would make it possible for the policing agency to brute-force itself into an iPhone 5C. This device belonged to Syed Farook, who, along with partner Tashfeen Malik, murdered 14 people in December 2015.
The FBI argues that access to Farook's phone could be useful in understanding who might have been behind the attacks. But Apple argues creating a back door would set a dangerous new precedent for its customers and for privacy.
Google has come out in favour of Apple's decision and Edward Snowden has described the story as the "most important tech case in a decade". Many more have weighed in - read on for more.
1. Apple vs FBI: Apple welcomes news FBI cracked San Barnardino shooter's iPhone
Image: Flickr / fw_gadget
In light of the FBI claiming it has now unlocked the device in question, an Apple spokesperson has said the case should "never have been brought".
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