A second law enforcement official who spoke on the condition of anonymity to reporters in a conference call said that a company outside the government provided the F.B.I. with the means to get into the phone used by Mr. Farook, which is an iPhone 5C running Apple’s iOS 9 mobile operating system. The official would not name the company or discuss how it was accomplished, nor would officials say whether the process would ultimately be shared with Apple.

Image Syed Rizwan Farook Credit... U.S. Customs and Border Protection, via Associated Press

Melanie Newman, a spokeswoman for the Justice Department, signaled in a statement that the broader battle over access to digital data from devices was not over.

“It remains a priority for the government to ensure that law enforcement can obtain crucial digital information to protect national security and public safety, either with cooperation from relevant parties, or through the court system when cooperation fails,” Ms. Newman said. “We will continue to pursue all available options for this mission, including seeking the cooperation of manufacturers and relying upon the creativity of both the public and private sectors.”

“This case should never have been brought,” Apple said in a statement, adding that it would continue to help with law enforcement investigations.

Given that the F.B.I. may never tell Apple how it forced open the iPhone, the company also said that it would “continue to increase the security of our products as the threats and attacks on our data become more frequent and more sophisticated.”

The conflict between Apple and the government erupted openly last month when a federal magistrate judge in California ordered the Silicon Valley company to help unlock the smartphone used by Mr. Farook. Timothy D. Cook, Apple’s chief executive, opposed the court order in a public letter, saying that “compromising the security of our personal information can ultimately put our personal safety at risk.”

The resistance led to heated rhetoric from both sides in dueling court filings, and the issue spurred debates — finding its way onto late night talk shows, and dividing the public. Apple and the Justice Department had been due in court last week in Riverside, Calif., and the case was seemingly headed toward appeals and even the Supreme Court.