In a series of videos, the man responsible for the deadly New Year’s attack in New Orleans discussed planning to kill his family and having dreams that helped inspire him to join ISIS, according to multiple officials briefed on the investigation.

The attack in New Orleans on Wednesday brought the group back into stark prominence. Fifteen people were killed when the driver of a truck slammed into New Year crowds on Bourbon Street — authorities said the suspect pledged allegiance to ISIS and flew its flag.