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, an online 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.
President Donald Trump later pledged to review foreign military training programmes in the US. More than 850 Saudi nationals are reported to currently to be in the country for such activities.
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.