Investigators had initially suggested others may have been involved in New Year’s Day attack

• New Orleans truck attack – latest updates

The FBI said on Thursday that it now believed the suspect acted alone in the truck attack in New Orleans on New Year’s Day that killed 15 and injured dozens more when a man drove a rented pickup truck into a crowd celebrating on busy Bourbon Street.

The chief suspect, 42-year-old US citizen Shamsud-Din Jabbar, was killed in the attack as he shot at police and was shot to death when law enforcement returned fire.