New Orleans/IBNS: The FBI Thursday said the US army veteran motivated by loyalty to the jihadist group Islamic State likely acted alone when he killed and injured dozens in a truck attack against a crowd of New Year revelers in New Orleans, media reports said.

Even as initial concerns predicted that Shamsud-Din Jabbar had accomplices, believed to be on the run, preliminary investigations show he was alone, FBI deputy assistant director Christopher Raia said.

"We do not assess at this point that anyone else was involved," Raia was quoted as saying by Agence France-Presse.

However, new evidence emerged revealing the details of the extent to which the US Army veteran's loyalty to the Islamic State was and his plans to cause mayhem in the attack.

The attack left 14 killed and injured more than 30 in the French Quarter district, which ended only after he was shot by police.

"He was 100 percent inspired by ISIS," Raia said, using an alternative name for the international jihadist group.

Before the attack, in which Jabbar slammed a rented Ford F-150 pickup into the crowd, he "posted several videos to an online platform proclaiming his support for ISIS," Raia said.

He also carried a black ISIS flag on the back of the vehicle.

In one video, Jabbar "explains he originally planned to harm his family and friends, but was concerned the news headlines would not focus on the 'war between the believers and the disbelievers.'"

Raia said that Jabbar had planted two homemade bombs in drink coolers in French Quarter streets. The bombs were viable but were made safe in time, he said.

Raia clarified that the total death count of 15 from Wednesday's carnage included 14 victims and Jabbar himself, who died after wounding two police officers in an exchange of gunfire, AFP reported.