Washington (CNN) - The Saudi military trainee who killed three US sailors and wounded several others in a terror attack last year on a military base in Pensacola, Florida, was in touch with a suspected al Qaeda operative, according to multiple US officials briefed on the matter.

US investigators uncovered the al Qaeda connection after the FBI broke through the encryption protecting the Saudi attacker's iPhones, the officials said. Attorney General William Barr and the FBI are expected to announce the finding Monday in a news conference.
Mohammed Alshamrani, a member of the Royal Saudi Air Force who had been training at Naval Air Station Pensacola, was killed by law enforcement during the attack.
A breakthrough on the shooter's phone encryption for now temporarily disarms a standoff between the Justice Department and Apple over national security and the limits of encryption and privacy. The government has complained in recent years that stronger encryption, without the ability of law enforcement to get court-ordered access to data, endangers the public.