The main gate at Naval Air Station Pensacola is seen on Navy Boulevard in Pensacola, Florida, March 16, 2016. Photo: US Navy / Patrick Nichols / Handout via Reuters.

The FBI cracked the iPhone encryption of the Royal Saudi Air Force trainee who killed three American sailors in a December attack at a US naval base in Florida and found evidence linking him to al Qaeda, Attorney General William Barr said on Monday.

The shooter, Second Lieutenant Mohammed Saeed Alshamrani, 21, was killed by law enforcement during the Dec. 6, 2019 attack.

He was on the base as part of a US Navy training program designed to foster links with foreign allies.

The Justice Department succeeded in unlocking the encryption on the shooter’s iPhone after Apple declined to do so, Barr told reporters on a conference call.

“The information from the phone has already proved invaluable,” Barr said.

Barr called on Congress to take action forcing Apple and other tech companies to help law enforcement agencies get through encryption during criminal investigations.

“Apple’s decision has dangerous consequences,” Barr said. “Many of the technology companies that advocate most loudly for warrant-proof encryption … are at the same time willing to accommodate authoritarian regimes.”

Apple did not immediately respond to a request for comment. In January, it said that it was working with the FBI on the investigation.

“We reject the characterization that Apple has not provided substantive assistance in the Pensacola investigation,” it said at the time. “Our responses to their many requests since the attack have been timely, thorough and are ongoing.”

In February, an audio recording purporting to be from al Qaeda in the Arabian Peninsula (AQAP) claimed responsibility for the fatal attack, but it provided no evidence.

Prior to the shooting spree, which also wounded eight people, the shooter posted criticism of US wars and quoted slain al Qaeda leader Osama bin Laden on social media.

“The evidence we have been able to develop … shows that the Pensacola attack was actually the brutal culmination of years of planning,” FBI Director Christopher Wray said on the same call, adding that evidence showed Alshamrani had been radicalized by 2015.

Barr has said the Saudi government did not have any advanced warnings of the shooting.

However, in January, Saudi Arabia withdrew its remaining 21 cadets from the US military training program and brought them back to Saudi Arabia, after the Justice Department’s investigation revealed that some of them had accessed child pornography or had social media accounts containing Islamic extremist or anti-American content.