Last month's deadly shooting at a navy base in Pensacola in Florida was 'an act of terrorism', US Attorney General William Barr declared on Monday.<br/> On December 6, a 21-year-old Saudi aviation student opened fire at sailors at the Naval Air Station Pensacola. killing three people and injuring eight more.<br/> The shooter was identified at the scene as Mohammed Saeed Alshamrani, a second lieutenant in the Royal Saudi Air Force, who was participating in a US training programme sponsored by the Pentagon.<br/> The attack was widely condemned by Saudi Arabia. The kingdom's ambassador to the US Reema bint Bandar, said at the time: "As a daughter of a former US military trained pilot, this tragedy is especially painful,"<br/> "The Saudi people are united in their condemnation of this crime. We stand in solidarity with our American friends during these difficult times."<br/> At a press conference in Washington on Monday, Mr Barr praised the co-operation of Saudi Arabia in the investigation into the incident.<br/> He added that the evidence shows that Alshamrani was motivated by extremist ideologies, including anti-American and anti-Israel sentiment.<br/> The attorney general said that on Sept 11, 2019 – the anniversary of the terrorist attacks on the World Trade Centre in New York – Alshamrani wrote on social media that "the countdown has begun", likely referring to his planned attack on the naval base.<br/> "During Thanksgiving giving he then visited the 9/11 memorial in New York City," Mr Barr added.<br/> Alshamrani was also critical on social media about American military action overseas and said he believed that violence was necessary to defend Muslim countries. The investigation found that he idolised deceased former Al Qaeda leader Anwar Al Awlaki. <br/> Mr Barr criticised Apple for failing to help the US government unlock Alshamrani's two iPhones that he had on him at the time of the attack. The Justice Department has been unable to access them due to encryption and password locks, despite having sought help from other federal agencies and experts.<br/> Unable to crack the security of the phones, which may contain critical information to the investigation, Mr Barr called on big tech firms to do more to help the Department of Justice with investigations.<br/> "So far Apple hasn't given us any substantive in assistance," he said.<br/> "We call on Apple and other technology companies to help us find a solution so we can better protect the lives of the American people and prevent future attacks."<br/> At the press conference, FBI deputy director David Bowdich echoed Mr Barr's sentiment.<br/> "We are not trying to weaken encryption to be clear and after all data security is a part of our mission, but even with the court order to date, we cannot access the information from these two phones in this investigation and countless of other investigations," he said.<br/> He added that the FBI was still searching for more information but evidence suggested that Alshamrani had acted on his own.<br/> "So far we have not identified any co-conspiracies, that he acted with anyone else or that he was affiliated with any specific group," he said.<br/> Mr Barr also said that the United States also expelled 21 Saudi military students training in America, following the investigation into the shooting. Mr Barr said that 17 of them posted extremist or anti-American content on social media.<br/> The attorney general said the cadets had returned to Saudi Arabia on Monday to face justice. The Justice Department reviewed whether any of the cadets should face charges, but decided that it not meet the standards for federal prosecution.<br/>