Update: we now have the suspect's name: Quazi Mohammad Rezwanul Ahsan Nafis, who in addition to Plan A had Plan B: "If Nafis felt his attack was about to be thwarted by cops, he would invoke the back-up plan, which involved a suicide bombing operation"
From CNN 
Quazi Mohammad Rezwanul Ahsan Nafis, 21, was arrested for allegedly attempting to detonate what he thought was a 1,000-pound bomb at the Federal Reserve Bank of New York in Manhattan, the Department of Justice and a U.S. attorney's office said in a press release.
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We now have some more detail about the plot to blow up the reserve bank from a press release that breaks down the criminal complaint filed against Quazi Mohammad Rezwanul Ahsan Nafis:
The Bangladeshi national allegedly came to the United States in January to carry out a terror attack on U.S. soil and said he had overseas connections to al-Qaeda. As he attempted to recruit others to join his cell, he tried to recruit someone who turned out to be an FBI source, the criminal complaint says.
Nafis initially had a few targets in mind, according to the complaint, including "a high-ranking U.S. official and the New York Stock Exchange." In the end, Nafis settled on the New York Federal Reserve Bank, federal officials said.
"In a written statement intended to claim responsibility for the terrorist bombing of the Federal Reserve Bank on behalf of al-Qaeda, Nafis wrote that he wanted to 'destroy America' and that he believed the most efficient way to accomplish this goal was to target America’s economy," the Justice Department press release said. "In this statement, Nafis also included quotations from 'our beloved Sheikh Osama bin Laden' to justify the fact that Nafis expected that the attack would involve the killing of women and children."
The "explosives that he allegedly sought and attempted to use had been rendered inoperable by law enforcement and posed no threat to the public," according to a statement from U.S. Attorney Loretta E. Lynch.
The plot came to light as an FBI undercover agent posed as an al-Qaeda facilitator, federal authorities say.
Nafis asked the undercover agent for 50-pound bags of what he thought were explosives, and then worked on putting together an explosive device, according to prosecutors.
"Nafis purchased components for the bomb’s detonator and conducted surveillance for his attack on multiple occasions in New York City’s financial district in lower Manhattan," a Justice Department press release describing the criminal complaint said. “Throughout his interactions with the undercover agent, Nafis repeatedly asserted that the plan was his own and was the reason he had come to the United States."
He met an undercover agent that supplied him with what he thought were explosives on Wednesday morning. After meeting up, they both traveled in a van to a warehouse, the Justice Department said.
That’s apparently when Nafis told the agent he had a "Plan B."
If Nafis felt his attack was about to be thwarted by cops, he would invoke the back-up plan, which involved a suicide bombing operation, the criminal complaint alleges.
When the pair arrived at the warehouse, Nafis began putting together what he thought was a 1,000-pound bomb inside the van. Then they drove together to the target: The New York Federal Reserve Bank. As they drove, he armed the purported by putting together the detonator and the explosives, the criminal complaint says.
The van was then parked next to the bank. The pair went to a nearby hotel, where Nafis apparently recorded a video statement meant to be shown to the American public in connection with the attack.
"We will not stop until we attain victory or martyrdom," he said, according to the criminal complaint.
He then tried, several times unsuccessfully, to detonate the device, which was actually inert explosives.
Nafis was then arrested.
A good portion of the sting operation was caught on tape, according to a source familiar with the investigation.
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NBC 4 New York  has learned that federal authorities have arrested a man they say was plotting to attack the Federal Reserve in New York City. The man is in custody in New York. Sources tell NBC 4 New York that he lives on Long Island. Law enforcement officials stress that the plot was a sting operation monitored by the FBI and NYPD and the public was never at risk.
- FBI, NYPD ARREST SUSPECTED TERRORIST IN NYC PLOT
- SUSPECTED TERRORIST IN PLOT TO ATTACK FEDERAL RESERVE OF NY
- FBI SAYS TWO FBI AGENTS ACTED AS `ACCOMPLICES' TO SUSPECT
- MARY GALLIGAN OF FBI NY OFFICE, CONFIRMS FED BOMB PLOT ARREST
- FBI PROVIDED DEFENDANT WITH FAKE EXPLOSIVES IN STING OPERATION
According to the report, the suspect drove a van he believed to be loaded with explosives from Long Island to Lower Manhattan. He then placed the van near the Federal Reserve and was then arrested by the FBI and NYPD.
The suspect, whom sources said is from the Jamaica Queens section of New York City, is currently in custody in New York. Sources say he was acting alone.
Middle Eastern man parked van he thought was filled with explosives outside N.Y. Fed this morning, then walked to nearby Millennium hotel and tried to set off bomb with cell-phone detonator, New York Post reports, citing unidentified law enforcement sources.
Suspect posted about Jihad online 3 months ago, told FBI agent he met online that he wanted to blow up
And "New York terror suspect is a 21-year-old Bangladeshi citizen who traveled to the U.S. in January to carry out terror attack."
At least all that tungsten gold lying on the Manhattan bedrock is safe and sound and John McClane will not be called out of retirement just yet.
It is unclear yet if Quazi hated America for its Federal Reserve or its collection of weapons grade Tungsten.