In a first-of-its-kind ruling, a U.S. magistrate has ordered Apple to assist the government in unlocking the iPhone of San Bernardino shooter Syed Rizwan Farook. The FBI is seeking information that may be on Farook's employer-issued phone as it investigates the Dec. 2 shootings that left 14 people dead. At the time of the attack, Farook and his wife, Tashfeen Malik, destroyed two personally owned cellphones and removed a hard drive from their computer. In what Apple described as a "customer letter" posted on its website late Tuesday, CEO Tim Cook said Apple will contest the judge's order.

NPR's Laura Sydell reports:

Last week, FBI Director James Comey told members of Congress that investigators had been unable to access Farook's phone. "It is a big problem for law enforcement armed with a search warrant when you find a device that can't be opened even when a judge says there's probable cause to open it," Comey said. In a prior case, Apple told a federal judge that it was "impossible" for the company to unlock devices running an operating system of iOS 8 or higher. In arguing this latest case, prosecutors said Apple could still disable security barriers in the phone's coding. Farook's phone runs iOS 9 and is configured to erase data after 10 unsuccessful password attempts. Forensics expert Jonathan Zdziarski said Apple might have to write custom code to comply with the court order. He also said that even without Apple's cooperation, federal investigators should be able to hack the phone with the assistance of the NSA and the CIA.