Main gate at Naval Air Station Pensacola
Main gate at Naval Air Station Pensacola Reuters

US Attorney General William Barr said on Monday that the shooting at a Naval air base in Pensacola, Florida, last month was an act of terrorism motivated by "jihadist ideology".

Three US sailors were killed when 21-year-old Mohammed Alshamrani, a member of the Royal Saudi Air Force who was training at Naval Air Station Pensacola, entered a building on base and "proceeded to walk around shooting down his unarmed victims in cold blood," Barr said at a press conference, according to CNN.

Alshamrani, who was killed by law enforcement during the attack, had a history of airing his anti-American, anti-Israel and jihadi messages views on social media, including in a post on September 11 stating that "the countdown has begun," and another post made two hours before the attack, Barr said.

During a 15-minute shooting spree, Alshamrani shot at a photo of President Donald Trump as well as a former president, according to FBI Deputy Director David Bowdich. He also made statements while he was shooting that were critical of American servicemen overseas, Bowdich said.

The FBI had said immediately after the shooting it is believed the shooter acted alone and that motive for the shooting was not yet established, though it added it was working, as it does in most mass shootings, on the presumption that it was an act of terrorism.

The Pensacola shooting drew immediate scrutiny to the system of accepting foreign military trainees on US bases. Barr defended the program on Monday, calling Saudi Arabia "an important military partner," and said that Saudi Arabia had been fully cooperative in the investigation.

No other co-conspirators have been charged in the shooting, and Barr said Monday that investigators did not find evidence that any of the shooter's friends or fellow trainees from Saudi Arabia had advanced knowledge that he was going to attack the base.

21 other Saudi trainees on US bases were, however, expelled on Monday after investigators uncovered "derogatory material." 17 of the Saudi trainees "had social media containing some jihadi or anti-American content," and 15 had contact with child pornography, Barr said.

Federal prosecutors evaluated each case and determined that none merited charges, Barr said, although the government of Saudi Arabia determined the material amounted to "conduct unbecoming" of a military officer, and the 21 trainees were disenrolled and returned on a flight to the kingdom Monday.