While much remains unknown about the man who carried out an attack in New Orleans on New Year’s and another who died in an explosion in Las Vegas the same day, the violence highlights the increased role of people with military experience in ideologically driven attacks, especially those that seek mass casualties.

By Tim Reid, Ned Randolph and Helen Coster WASHINGTON/NEW ORLEANS (Reuters) -Law-enforcement officials in U.S. cities were beefing up security on Thursday after a deadly attack in New Orleans and an explosion outside a Trump hotel in Las Vegas raised fears of more threats in a month packed with large-scale public events.

US officials say there’s no sign that Islamic State directed a deadly New Year’s attack in New Orleans. But early evidence that the attacker drew inspiration from the group highlights its ability to spur mass violence despite multinational efforts to wipe it out.

Investigators now believe the driver who barreled through a crowd of New Year’s Day revelers in New Orleans acted alone in what the FBI is calling an act of terrorism.

A U.S. Army veteran who drove a pickup truck into a crowd of New Year’s revelers in New Orleans, killing 15 people, had posted videos to social media hours before the carnage saying he was inspired by the Islamic State group and expressing a desire to kill,