The Saudi national, who carried out the attack on the US naval air station in Pensacola last week, watched videos of mass shootings at a dinner party the night before he went on a shooting spree, a source familiar with the investigation told The New York Times.
As identified by the US Federal Bureau of Investigation (FBI), Mohammed Alshamr -- a 21-year-old second lieutenant in the Saudi Arabian air force, along with three other Saudi military trainees visited New York City before the attacks at the Naval base, including several museums and Rockefeller Center, according to the person.
Investigators are seeking to determine whether the trip was a tourist excursion during the Thanksgiving holiday week in New York, or whether the Saudi trainees had other motives or met with other people there.
Three people were killed and eight others sustained injuries in the attack on Friday.
The gunman did not have any apparent ties to international terrorist groups, according to a senior American official was quoted as saying on the condition of anonymity.
Alshamr, who was killed by a sheriff's deputy while responding to the attack, initially entered the United States in 2017, when his training began at the Pensacola site, Pentagon officials were quoted as saying.
After his initial arrival in the country, he attended language school at Lackland Air Force Base in San Antonio, Texas, the officials added and took classes in English and aviation.
He would travel back to home to Saudi Arabia during school breaks, but after his return in February, friends and colleagues noticed that he had become more religious, the officials added.
Meanwhile, six other Saudi nationals were detained for questioning near the scene of the shooting, which took place over two floors in a classroom on the base.
Three of the Saudis, who were detained, were seen filming the entire incident, the source said. However, the detainees confirmed the investigators that they just happened to be there at that time and wanted to capture the moment, the person added.
However, it is still not known whether the six Saudis detained were students in the classroom building, the person said.
Saudis have received training at the Pensacola site since the 1970s. As of Friday, there were 852 Saudis in the US for Pentagon-sponsored training related to security cooperation, representing 16 per cent of the 5,181 students from 153 countries in these programs, Defense Department spokesman Chris Garver said, as cited by Washington Post.
The Saudi Foreign Ministry has expressed "its deep distress" following the shooting and offered "its sincere condolences to the victims' families".
( With inputs from ANI )