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The four men accused of plotting to bomb New York City synagogues and shoot down military airplanes with missiles are down-and-out ex-convicts living on the margins in a faded industrial city.

One is a petty criminal who spent a day in 2002 snatching purses and shooting at people with a BB gun from an SUV. His lawyer calls him "intellectually challenged."

Three have histories of drug convictions, one of them for selling narcotics in a school zone. The man prosecutors portrayed as the instigator of the scheme said he smoked pot the day he planned to blow up the temples.

They went to Wal-Mart for cameras to photograph their targets and had to call around to various contacts to get guns, prosecutors said.

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But if they sometimes seemed amateurish, the men were dangerous people fueled by their hatred for Jews and America, prosecutors said. The plotters managed to get their hands on what they thought were lethal explosives and a surface-to-air missile system, only to find out that they were inert devices supplied by the FBI in a sting operation.

"It's hard to envision a more chilling plot," assistant U.S. attorney Eric Snyder said. "These are extremely violent men."

With an informant's help, the FBI monitored the plot every step of the way, including with video and audio surveillance of a home in Newburgh where the conspirators gathered, according to a criminal complaint.

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The arrests follow a long line of homegrown, headline-making terror plots since Sept. 11 that never came close to reality because the FBI inserted itself in early stages. Authorities have broken up plots with targets including the Sears Tower in Chicago, the Herald Square subway station in Manhattan, underground gas pipes at John F. Kennedy International Airport, the Fort Dix military base in New Jersey and tunnels underneath the Hudson River.

James Cromitie, David Williams, Onta Williams and Laguerre Payen were calm as they appeared in court Thursday, their hands shackled, to answer charges of conspiracy to use weapons of mass destruction within the U.S. and conspiracy to acquire and use anti-aircraft missiles. They did not enter pleas and were held without bail; they face life in prison if convicted.

Besides destroying the two synagogues in the heavily Jewish Riverdale section of the Bronx, they intended to shoot down planes at the Air National Guard base in Newburgh, about 50 miles north of New York City, prosecutors said.

FOX 5 VIDEO: Update on Foiled Terror Plot.

Relatives said the defendants were struggling men who worked at places such as Wal-Mart, a landscaping company and a warehouse when they weren't behind bars. Payen's lawyer said he was on medication for schizophrenia and has "a very low borderline" IQ.

David Williams' relatives were floored by the allegations against a man they knew as a good father to his 7-year-old daughter and newborn son.

"You don't raise your children to be terrorists," said Aahkiyaah Cummings, his aunt. "I don't know that guy that was arrested."

Just four years ago, Williams, now 28, told a parole board that prison was a wake-up call after his conviction on drug and weapons charges — drugs he said he sold because he was making only $150 a week in his job.

Onta Williams, 32, and Cromitie have also served prison sentences for drug convictions — Cromitie said in court he had used marijuana as recently as Wednesday. He said he was 55, though law enforcement records give his age as 44.

Payen, 27, did time for attempted assault — in 2002, he and others fired a BB gun out an SUV window, hitting two people in the head. He snatched purses from two women later the same day, said state Division of Parole spokeswoman Heather Groll.

Payen appears to be a Haitian citizen, while the other three are Americans. The Williamses are not related.

New York City Police Commissioner Raymond Kelly said he believed the defendants knew each other from their time behind bars. Relatives said Payen, David Williams and Onta (AWN'-tay) Williams were introduced to Islam in prison — a trend in prisons around the country in recent years.

"The Onta I know wouldn't do something like this, but the new Onta, yeah," said Richard Williams, an uncle. "He wasn't raised this way. All this happened when he became a Muslim in prison."

He said his nephew, who loaded tractor-trailers at a warehouse, had been shaken by his mother's death in 2006 and a separation from his wife. She has custody of his three children.

Payen was apparently staying in a rundown house that neighbors say was known as a home for parolees. Penniless and jobless, he had been fighting deportation and seeking custody of his 3-year-old son, said Hamin Rashada, an assistant imam at the Masjid al-Ikhlas mosque, where authorities say the informant first met Cromitie in June 2008.

Cromitie was burning with anger about the U.S. war in Afghanistan, where his parents had lived before he was born, according to the criminal complaint. He told the informant he was interested in jihad and "doing something to America" and was crestfallen that "the best target (the World Trade Center) was hit already," the complaint said.

In the same conversation, Cromitie said: "I hate those mother———-, those f——— Jewish b——— .... I would like to get (destroy) a synagogue," according to the complaint.

In one conversation, Cromitie said he longed to shoot Jews in the head as they walked on the street near a synagogue, the informant told authorities. In another conversation with the informant, Onta Williams said the U.S. military was killing Muslims, "so if we kill them here with IEDs and Stingers, it is equal," according to court papers.

A woman who answered the phone at a Bronx listing for several of Cromitie's relatives said she didn't want to speak about him and hung up. No one answered the door at his Newburgh address, but neighbor Luis Pena said Cromitie was "a real nice guy."

Cromitie told the informant last July that he wanted to join Jaish-e-Mohammed, a Pakistani terrorist group with which the informant claimed to be involved, the complaint said. Authorities say Jaish set up training camps in Afghanistan under the Taliban, and several senior operatives were close to Osama bin Laden.

By December, Cromitie was asking the informant to supply explosives and surface-to-air missiles. The suspects obtained the weapons — not knowing they were disabled — earlier this month, according to the complaint.