“We were going to use the black powder and other materials to make an explosive,” Toro told a judge Monday in U.S. District Court in Manhattan.

Yet even after the guilty pleas, the brothers’ motive for building a bomb and what their target might have been remained unclear. “I just want you to know that I had no intention of using it, let alone on anyone or anything,” Toro told Judge Richard M. Berman. Tyler Toro also contended that he had never intended to harm anyone.

The investigators recovered handwritten diary entries in the men’s apartment that referred to an operation code-named Flash. They also found a yellow backpack containing a purple index card that read, in all capital letters, “Under the full moon the small ones will know terror.”

The brothers did not appear to be inspired by international terrorist groups like the Islamic State, but the government has asserted that the threat the men posed was real. Geoffrey S. Berman, the U.S. attorney in Manhattan, said Monday after the men pleaded guilty that the device they sought to build “could have caused great damage.”

At a bail hearing, one prosecutor, Elizabeth Hanft, said there was a text-message exchange between the brothers about the October 2017 mass killing of concertgoers in Las Vegas.

Tyler Toro texted his brother that the shooter in the Las Vegas massacre had a police scanner, and that they should invest in one, too.

“Copy,” Christian Toro responded. “I see a couple on Amazon.”

The investigation that led to the men’s arrest stemmed from a bomb threat that was called into Harlem Prep High School, a charter school where Christian Toro taught, nearly a year ago, according to a criminal complaint and statements by law enforcement officials at the time.

The police arrested a 15-year-old female student and charged her with making the threatening call. Toro resigned Jan. 9, and three weeks later he was charged with rape after being accused of having a sexual relationship with the same student. It was during the rape investigation that New York police detectives learned Toro had paid students to harvest powder from fireworks.

After Christian Toro resigned, Tyler Toro returned to the school a laptop that his brother had used in connection with his job, according to the complaint, which is signed by an FBI special agent, Seth Yockel. A copy of a book with instructions for making explosive devices was found on the computer’s hard drive, the complaint said.

Christian Toro later told investigators that he had come across the book while researching the 2013 Boston Marathon bombings and had only looked at its table of contents, the complaint noted.

A search of the brothers’ apartment turned up what Hanft called “a veritable trove” of chemicals and other bomb-making materials, including a box containing 20 pounds of iron oxide, 5 pounds of aluminum powder, 5 pounds of potassium nitrate, a jar of explosive powder, a box of firecrackers and a bag containing scores of metal spheres of varying sizes, which the authorities said could become projectiles in a blast.

The students who were paid to dismantle fireworks visited the men’s apartment between October 2017 and January, the complaint said.

The men are to be sentenced March 26.

The New York Times

Benjamin Weiser © 2018 The New York Times