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 an “act of terrorism” in the truck attack in New Orleans on New Year’s Day that killed 14 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, bringing the total fatalities from the incident to 15, with more than 35 injured.