This story has been updated since it first appeared online on Nov. 1.
An East Hampton man accused by federal agents of trafficking in child pornography is being held without bail, facing a possible sentence of 15 years in federal prison if convicted.
Michael S. Bonnet, 28, a registered sex offender, was arrested on the morning of Oct. 30 by combiined elements of the Long Island Child Exploitation Task Force, headed up by the Federal Bureau of Investigations, said Kelly Langmesser, a spokeswoman for the bureau. Mr. Bonnet was arraigned that afternoon by William D. Wall, a United States magistrate judge in the Eastern District of New York, who had issued the warrant for his arrest the day before.
In a complaint filed against Mr. Bonnet, Danielle Messineo of the F.B.I., alleged that on Feb. 24 and 25 of this year Mr. Bonnet had sent an undercover agent pornographic images depicting children as young as under 5 engaging in either masturbation alone or in sexual intercourse with adults.
Ms. Langmesser lauded the work of Agent Messineo. "She is an unsung hero," who, on her own time and free of charge, leads seminars teaching children how to avoid sexual predators online.
Ms. Langmesser said that the arrest was made with the assistance of the Suffolk County Police Department, as well as the Suffolk County Probation Department, whose officers "were instrumental in making this arrest happen."
The arrest itself was originally planned for Oct. 31, but was moved up a day after a report about the investigation was published online, Ms. Langmesser said.
Agent Messineo, who has been with the F.B.I.'s Internet Crimes Against Children squad since 2003 and with the bureau for 18 years, said in the complaint against Mr. Bonnet that a member of her squad, identified only as "UC," had posted an advertisement on a Web site dedicated to "human sexuality" seeking "Yng HC Pics," meaning young, hardcore pictures.
The ad, which was posted on Feb. 24, read, "Looking to trade YNG hardcore pics or vids. If u send me soft stuff, older or modeling pics, I will ignore you . . . Yngr=better."
According to the complaint, Mr. Bonnet responded almost immediately with an e-mail. Using an alias, Bob Jones, he allegedly wrote, "Still want to trade? What you looking for?"
Then, Agent Messineo said, Mr. Bonnet wrote in a subsequent e-mail, "Yes I know just hoping your not a cop or something don't need trouble could you maybe send one so I know your not?"
The next day, the undercover agent wrote an e-mail to Mr. Bonnet saying that "Bob Jones" would need to "send to receive." According to Agent Messineo's complaint, that is when Mr. Bonnet sent the first image, later determined to have come from his cellphone, of a prepubescent girl masturbating with a sex toy.
The agent said in the complaint that she had been extensively trained over many years to recognize the difference between actual images and doctored or computer-generated ones, and to be able to discern whether the subject was, in fact, a child. Such was the case, she said, for the images Mr. Bonnet sent.
To keep the sting going, the undercover agent then sent an e-mail containing a file that was deliberately corrupted so that it could not be viewed. It appeared to contain a pornographic video, but was in fact blank.
"Bob Jones" sent the undercover agent two more images, according to the complaint, one of them of an adult male engaged in sexual act with a girl under the age of 5, Ms. Messineo said.
The complaint states that the task force tracked the e-mails back to Mr. Bonnet's cellphone "using publicly available data."
The F.B.I. also reportedly found three postings by Mr. Bonnet on topix.com that agents believe were requests to trade pornography online, in which he gave an e-mail address of firstname.lastname@example.org, with a posting location of East Hampton.
Again, using online tools available to the general public, the task force searched for an "M. Bonnet." There was only one in East Hampton, the complaint says, Michael S. Bonnet, with a home address of 29 Cosdrew Lane. The complaint notes that Mr. Bonnet is a registered sex offender, having been convicted of sexually abusing a 14-year-old girl in 2008. That conviction would explain the Probation Department's knowledge of Mr. Bonnet.
The task force interviewed Mr. Bonnet on Oct. 24, after reading him his Miranda rights, which, they said, he waived.
According to the complaint, Mr. Bonnet admitted to sending the images, as well as actively trading pornographic images from his Samsung Galaxy 4 smartphone, which contained over 100 such images. He allegedly told the F.B.I. that he had more images on another cellphone, and that he would masturbate as he traded the images. Some pictures "depicted children whose identities are believed to be known to law enforcement," according to complaint.
Under federal criminal guidelines, the prosecution now has 30 days from the time of Mr. Bonnet's arraignment to obtain an indictment from a grand jury or be forced to release him.
Mr. Bonnet was represented in court on Oct. 30 by Randi L. Chavis, a federal defender, the federal-level equivalent of a Legal Aid attorney. Contacted by phone, Ms. Chavis declined to comment on the case.