What to Know Christian Toro, a former teacher at a Harlem high school, was trying to build bombs with his brother in their apartment, authorities say

They paid students at Christian Toro's Harlem school $50 an hour to break down fireworks and collect powder from them, the complaint says

The inquiry began when Christian Toro resigned from the school and his brother returned a school laptop with a bomb-making manual on it

A former teacher at a Harlem charter school stockpiled bomb-making materials and paid students to break down fireworks to extract gunpowder for the explosives, authorities say.

Christian Toro and his brother, Tyler Toro, were arrested by the FBI Thursday morning after authorities found a bomb-making manual on the teacher's school-issued laptop, 30 pounds of chemicals and household materials used to create explosives in their apartment, a diary that referenced "operation flash" and a handwritten note in a bookbag that said "under the full moon the small ones will know terror."

Authorities said the pair had been compiling the bomb-making materials since October, but law enforcement sources said the pair had not made any specific threats, completed any devices or chosen targets. They also had not been on law enforcement organizations' radars before the investigation, police said Thursday.

"There is no immanent threat to New York City at this time," Mayor Bill de Blasio said in a news conference Thursday night.

They both face federal bomb-making counts, and Christian Toro is additionally charged with distributing explosive materials to a minor. They both pleaded "not guilty" in federal court Thursday; attorney information for the pair wasn't immediately available.

Two law enforcement sources told News 4 Christian Toro was having an inappropriate relationship with a teen girl at a Democracy Prep high school, where he worked, and that he had resigned shortly after the student called in a threat on Dec. 4.

The student was later arrested, according to a complaint. Christian Toro was also arrested in January on rape charges, though it's not clear if it is related to the relationship with the student.

After he resigned, Tyler Toro returned Christian Toro's school-issued laptop to the school. A technical specialist there found a found copy of a book providing instructions on how to assemble bombs.

"After he resigned Democracy Prep, did a routine review of his laptop and was deeply disturbed by suspicious content," a spokeswoman for the school said. "We immediately notified law enforcement of the content on Mr. Toro's laptop."

The school alerted law enforcement, and FBI agents and other authorities went to the brothers' Bronx apartment on Feb. 8. The two and a female relative told agents he hasn't meant to download the explosives manual and that he had been researching the 2013 Boston Marathon bombings, according to the complaint.

"Some good people stepped forward and that information that was crucial to law enforcement," de Blasio said of the school officials.

Then, on Wednesday, FBI agents went to speak with students at the Harlem school and learned that at least two had gone to Christian Toro's apartment to break apart fireworks and store the gunpowder in containers. The former teacher paid the students $50 an hour for their work, the complaint alleges.

A search warrant was executed at the apartment Thursday, and authorities allegedly found a dozens of pounds of household materials and other chemicals used to build improvised explosives in a bedroom.

Among the items, authorities found 20 pounds of iron oxide and five pounds of aluminum powder, which form thermite when combined; five pounds of potassium nitrate; two pounds of confectioner's sugar, which can be used as fuel for making explosive devices; a glass jar of black explosive powder; a cardboard box of firecrackers; a plastic container of apparent thermite; a small container of potassium nitrate; and a bag of metal spheres, which can be used as shrapnel.

They also found a diary with Tyler Toro's name in it, which said "Christian arrested" and "If you're registered as a sex offender, things will be difficult. But I am here 100 percent, living, buying weapons. Whatever we need," according to the complaint.

The diary also talked about having thrown away all the evidence of something code-named operation "Flash," proclaimed "we are the twin Toros" and threatened retribution if anyone would "strike us now," authorities said. It added, "I hope this doesn't turn into a scene from Goodfellas," they said.

Authorities also found a yellow backpack in the living room of the apartment, which contained a purple index card with a handwritten note that said, "Under the full moon the small ones will know terror." The backpack belonged to Christian Toro, the agents learned.

"We don't know at this point in the investigation... the full breadth of what these materials mean," said John Miller, the NYPD's deputy commissioner of intelligence and counter-terrorism.