New Orleans attack latest: Suspect's travel to Egypt under investigation | Live updates

Attorney General Merrick Garland confirmed the FBI is investigating the incident as an act of terrorism. He said the the Justice Department's National Security Division, and the U.S. Attorney's Office for the Eastern District of Louisiana are working with local law enforcement and "will deploy every available resource to conduct this investigation."

"The country woke up this morning to news of a terrible tragedy in New Orleans that killed at least 10 people and injured many more," Garland said in a statement. "My heart is broken for those who began their year by learning people they love were killed in this horrific attack, and my prayers are with the dozens who were injured, including the New Orleans Police Department Officers who risked their lives to save others."

Leading up to the holidays, federal law enforcement and intelligence had warned police around the country that low-tech vehicle ramming was a key area of concern and that they needed to prepare -- and that was before the German Christmas market attack on Dec. 20, in which five people were killed and hundreds were injured.

In a Dec. 9 assessment for the Times Square New Year's Eve celebration, federal and local agencies wrote: "We remain concerned about the use of vehicle ramming against high-profile outdoor events...Vehicle ramming has become a recurring tactic employed by threat actors in the West, marked by a continued interest by (terrorists, extremists) and lone offenders in targeting crowded pedestrian areas."

New Orleans police are conducting a grid search of the French Quarter for any possible additional IEDs, New Orleans Parish District Attorney Jason Williams told ABC News.

This, after explosive devices discovered in and around the scene on Bourbon Street were apparently found to be viable, multiple law enforcement sources also tell ABC News. Several controlled detonations have taken place, ABC News Aaron Katersky reported.

Officers are looking into parked cars, trash cans and along every nook and cranny, Williams said.

Authorities are also working to determine whether the deceased suspect had help with a three-pronged attack involving a vehicle ramming, gunfire and improvised explosives, according to the DA.

Attorney General Merrick Garland said the FBI is investigating this matter as an act of terrorism.

President-elect Donald Trump released a statement on the New Orleans attack calling it an "act of pure evil."

"Our hearts are with all of the innocent victims and their loved ones, including the brave officers of the New Orleans Police Department," Trump wrote.

He then indicated his administration will support the City of New Orleans with the investigation.

Vice President-elect JD Vance also reacted on social media.

"Heartbreaking violence last night in New Orleans. Such a beautiful and great American city. May God bless the victims and their families."

Witnesses described scenes of carnage in the wake of an attack early Wednesday morning on Bourbon Street in New Orleans that left 10 killed and 30 injured.

"We heard a 'pop, pop, pop, pop' sound, followed by a sound that sounded like fireworks going off, like a big firework all at once, and it turned out that was the crash," said Paul S., who asked ABC News to withhold his full name.

Paul said he peeked through the curtains to see what was occurring and saw police officers telling people in buildings to stay inside. He then went onto the balcony and started recording the aftermath of the attack.

Viewer Discretion Advised: Some descriptions may be graphic

"There's litter all over the sidewalks, and then there were bodies laid up next to garbage cans and people rushing to give aid," he said. "There were...these really bright lights out on Bourbon Street and that illuminated the scene where you could look up and down a block and see it completely empty except for the bodies that were on the ground."

Another witness, Jimmy Cothran, told ABC News' Morgan Norwood he and his group ducked into a Bourbon Street nightclub when the commotion began.

"Body after body mangled just as far as you could see. We counted 10, and at least six were instantly clearly deceased. Some were very clearly deceased, but others were yelling out. ... It's a lot to process," he said.

Cothran added that he saw some bodies in the street that bore tire marks.

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