The New Orleans attacker tried to use high explosives that could have killed hundreds

The New Orleans truck bomber built two bombs using what investigators believe was an explosive substance so powerful they could have sprayed shrapnel hundreds of yards, potentially killing or injuring hundreds of people.

The bombs did not detonate on New Year’s Day. But experts say devices Shamsud-Din Jabbar built with a compound believed to be RDX would have had devastating effects if not for an amateurish blunder.

“As horrible as it is that he killed and injured all these people, it could have been exponentially worse in the truest sense of the word if these devices had actually worked,” said Scott Sweetow, a retired director of the Bureau of Alcohol, Tobacco, firearms and explosives and former director of the FBI’s Terrorist Explosive Device Analytical Center. “You would be looking at literally hundreds of victims.”

A bomb made with RDX detonated in a tourist section of New Orleans would be equivalent to several hand grenades thrown into a crowded street, Sweetow said.

“It would have been an absolute carnage,” he added.

The bombs failed to detonate because Jabbar used the wrong device to detonate the explosives, federal law enforcement officials have said.

He used an electric match which could set off a typical pipe bomb made with powder explosives. But a compound like RDX is far more difficult to offset. It is considered a high explosive material, meaning it will not detonate without a primary explosion occurring near it – initiated by what is known as a blasting cap or detonator.

Three explosives experts interviewed by NBC News said they were amazed that Jabbar apparently knew how to use a little-known compound more powerful than TNT, but not how to detonate it.

“It just doesn’t make sense,” said Anthony May, a retired ATF agent who also worked as an Army explosives enforcement officer in Afghanistan.

By using RDX, experts say Jabbar mimicked the tactics of terrorist groups operating in the Middle East, where it is far easier to get hold of. The vast majority of bombings in the United States involve powder explosives, which are easier to make and far less powerful.

“What’s most concerning to me is that other people might try to do this now,” said David Hyche, a former ATF agent who is now police chief in Calera, Alabama.

Jabbar, 42, a Texas military veteran inspired by the Islamic State terror group, killed 14 people and injured dozens when he drove a rented pickup truck down a blocked-off section of Bourbon Street around 3:15 a.m. on Jan. 1. After carving a three-block path of destruction, he was shot and killed in a gun battle with the police.

About an hour earlier, Jabbar had placed his homemade bombs in two coolers and placed them on Bourbon Street, the famous party area in the heart of the French Quarter. It remains unclear whether he resorted to the truck attack because the bombs failed to detonate, or whether using the truck to kill was always part of his plan. Jabbar also had a handgun and a semi-automatic rifle with a privately made silencer, according to police.

At his Houston home, investigators found explosive materials that field tests identified as RDX. They also found explosive materials in a home he rented in New Orleans that tested initially identified as R-Salt, an explosive chemically similar to RDX. But the ATF said Sunday it now believes more thorough lab tests will show it was also RDX.

RDX is not easy to come by in the US. A military-grade explosive, it is also used for specialized purposes by demolition and mining companies and can only be purchased with a federal license. Criminals have been known to get their hands on stolen RDX, but several experts told NBC News they suspect Jabbar synthesized it himself — a time-consuming and highly dangerous endeavor.

That theory is based on footage recorded inside Jabbar’s Houston home of the New York Post, which showed a property receipt with items seized by federal investigators, including common laboratory supplies and precursor chemicals such as acetone, sulfuric acid and potassium nitrate.

“There is no indication that he had the knowledge to do this on his own,” said Sweetow, the former ATF and FBI official. “So he had to have either received information from outside sources or done considerable research on the Internet.”

Terrorist groups in the Middle East have bomb makers who synthesize their own high explosives, but this is rarely seen in the United States. The two most famous cases of this are the World Trade Center bombing in 1993 and the Oklahoma City Federal Building bombing in 1995.

Had Timothy McVeigh, the Oklahoma City bomber, used RDX, the attack would have been even more catastrophic, experts said.

“You wouldn’t have had a building blown down,” said Hyche, the former ATF agent turned police chief. “You’d have more buildings blown down.”

Building a bomb with RDX is also more challenging and dangerous.

“Most people don’t have the skills to do that and they’re not willing to follow a recipe,” Sweetow said. “People kill themselves all the time trying to make this because they’re not that good of a chemist.”

The retired ATF officials said investigators are almost certainly looking into how Jabbar got the knowledge to use a compound like RDX. Was he working directly with a member of ISIS or another terrorist group? Or did he find instructions in an obscure corner of the internet?

“If someone told him how to do this, where are they?” Sweetow said. “And is this part of a trend?”