The Saudi gunman who attacked a Florida navy base on Friday played videos of mass shootings at a dinner beforehand, US media reports say.
Mohammed Alshamrani – who was training at the Pensacola base – killed three sailors before being shot dead.
The US Navy said the sailors “showed exceptional heroism and bravery in the face of evil”.
They were named as Joshua Kaleb Watson, 23, Mohammed Sameh Haitham, 19, and Cameron Scott Walters, 21.
Several Saudi trainees have reportedly been held for questioning.
Authorities have not alleged that they were involved in the attack, which took place across two floors in a classroom on Friday morning.
The gunman played the mass-shooting videos to others at a dinner earlier in the week, several US media outlets report, quoting an anonymous official briefed on the investigation.
A Twitter user appearing to match Alshamrani’s identity had also made a series of anti-US posts before the shooting, a jihadist monitoring group says.
But US Defence Secretary Mark Esper said on Saturday that he would not label the incident “terrorism” at this point.
Speaking at the Reagan National Defense Forum in California, he said investigators must be allowed to do their work.
The Florida attack was the second shooting to take place at a US military base last week. Two days earlier, a US sailor shot dead two workers at the Pearl Harbor military base in Hawaii.
What happened on Friday?
Authorities were alerted to the shooting at the Pensacola base at 06:51 (12:51 GMT).
It took place across two floors of a classroom building and ended when a sheriff’s deputy killed Alshamrani.
Eight people were also injured in the shooting, including two officers, who are expected to recover.
Family members of Joshua Kaleb Watson said he was shot several times but made it out of the building to alert first responders.
On Facebook, his brother Adam Watson wrote: “He died a hero and we are beyond proud but there is a hole in our hearts that can never be filled.”
Capt Tim Kinsella, the base’s commanding officer, said of the three sailors killed: “When confronted, they didn’t run from danger; they ran towards it and saved lives.”
Why were Saudis at the US base?
The Pensacola base has long offered aviation training to foreign military.
Saudi pilots started training at the Pensacola base in 1995, alongside other personnel from Italy, Singapore and Germany.
Cpt Kinsella Jnr said that about 200 international students were enrolled in programmes there.
According to its website, the base employs more than 16,000 military and 7,400 civilian personnel.
Alshamrani was a second lieutenant in the Saudi Air Force, US officials say.
What has the reaction been?
Saudi Arabia is a key US ally in the Middle East and President Donald Trump said that the Saudi king called him after the attack to “express his sincere condolences and give his sympathies to the families and friends of the warriors who were killed”.
Mr Trump said King Salman told him that “this person in no way shape or form represents the feelings of the Saudi people who love the American people”.
In a statement, the Saudi foreign ministry called the attack “horrific” and said it would provide “full support” to the investigation.
However, Florida Governor Ron DeSantis said Saudi Arabia owed “a debt here, given that this was one of their individuals”.
He added: “There’s obviously going to be a lot of questions about this individual being a foreign national, being a part of the Saudi air force and then to be here training on our soil.”