The Saudi military trainee who killed three and wounded several others in a shooting at the Naval Air Station Pensacola in Florida last year had links to al-Qaeda, the FBI and Department of Justice announced Monday.

U.S. officials said investigators had found links to a suspected al-Qaeda operative on the phone of shooter Mohammed Alshamrani, a member of the Royal Saudi Air Force, who was killed by law enforcement during the attack. The shooting was the first deadly attack committed on American soil with the aid of al-Qaeda since the September 11, 2001, attacks.

“The FBI finally succeeded in unlocking Alshamrani’s phones. The phones contain information previously unknown to us that definitively establishes Alshamrani’s significant ties to al Qaeda in the Arabian Peninsula — not only before the attack, but before he even arrived in the United States,” Attorney General Barr said during a Monday press conference.

The reports come after investigators were able to decrypt Alshamrani’s two iPhones. While investigators had initially suspected Alshamrani of jihadist and anti-American motives, the Justice Department had been unable to decrypt the trainee’s two phones, and manufacturer Apple had refused to aid the DOJ citing potential damage to data security.

“We have always maintained there is no such thing as a backdoor just for the good guys,” the company said in a January 14 statement after Attorney General William Barr criticized the company. “Backdoors can also be exploited by those who threaten our national security and the data security of our customers . . . We feel strongly encryption is vital to protecting our country and our users’ data.”

Barr had earlier expressed frustration with Apple regarding the investigation.

“So far Apple has not given us any substantive assistance,” Barr said at a press conference. “This situation perfectly illustrates why it is critical that investigators be able to get access to digital evidence once they have obtained a court order based on probable cause . . . We call on Apple and other technology companies to help us find a solution so that we can better protect the lives of Americans and prevent future attacks.”