The FBI arrested a 20-year-old American Jewish man for posing as an Islamic State extremist, calling for terrorist attacks, claiming to be planning attacks in Australia and the United States, and providing information on bomb construction to a second party. According to the Sydney Morning Herald, the same man, who it named as Florida resident Joshua Ryne Goldberg, also posed as a respected Australian lawyer in April to maliciously post a racist blog post on The Times of Israel.

Goldberg was arrested at his home by Florida police for alleged “distribution of information relating to explosives, destructive devices, and weapons of mass destruction,” the Herald reported Friday.

He had allegedly posed online as “Australi Witness,” and used the persona to urge jihadi attacks. He faces up to 20 years in jail if convicted.

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Though the Sidney Morning Herald described Goldberg, who lives with his parents in Jacksonville, as having “no real-world links with extremism,” federal officials said they were taking his actions very seriously.

“It will also be alleged that this person provided information over the Internet in an attempt to facilitate and encourage terrorist acts in Australia,” an official statement said.

Australian Federal Police confirmed they had helped the FBI track down Goldberg.

The Herald said “Australi Witness” had allegedly distributed pictures of a bomb he was building which he said had “2 lbs of explosives inside.”

It said he was accused of instructing someone on how to make a bomb from a pressure-cooker, and to fill it with nails and other metal pieces dipped in rat poison.

In April, Goldberg also allegedly posed online as prominent Australian lawyer Josh Bornstein, and posted a hateful and racist post in Bornstein’s name on The Times of Israel. The post was quickly removed by The Times of Israel. Goldberg had opened a blog on the website some weeks earlier, appropriating Bornstein’s name, biography, photograph and taking steps to lend the blog credibility.

He initially published a series of inoffensive posts, which turned out to have been taken from Bornstein’s articles elsewhere on the Internet. But after establishing his credibility on The Blogs platform, the imposter published an inflammatory blog post calling for the “extermination” of Palestinians. The post was also copied to an online archive with the intent of causing maximum harm. The Times of Israel swiftly removed the blog post and the entire blog. The Times of Israel also published an article expressing dismay that it “fell victim to such a malicious and hateful hoax,” apologized to Bornstein, and filed a complaint with the police.

According to the Herald report on Friday, Goldberg boasted when confronted that he had avoided detection, saying, “That guy has no idea. He thinks [online radical right-wing website] Daily Stormer did it.” He said he had also sought to obtain Bornstein’s address, to “freak him out even more.”

Posing as Australi Witness, Goldberg also allegedly urged followers to target Australian cartoonist Larry Pickering, who has previously depicted the Prophet Mohammad, the Herald reported Friday.

“The Australi Witness persona fooled members of the international intelligence community as well as journalists,” the Herald report said, “with well-known analyst Rita Katz of SITE Intelligence Group saying the ‘IS supporter’ held a ‘prestige’ position in online jihadi circles and was ‘part of the hard core of a group of individuals who constantly look for targets for other people to attack.'”

US officials told the Herald that Goldberg had admitted to distributing information on bomb-making and “further admitted that he believed the information would create a genuine bomb.

“An affidavit sworn at the time of the arrest says that, between August 19 and August 28, Mr Goldberg ‘distributed information pertaining to the manufacturing of explosives, destructive devices, or weapons of mass destruction in furtherance of an activity that constitutes a Federal crime of violence,'” the Herald reported.

It went on: “US Attorney Lee Bentley III said Goldberg instructed a confidential source how to make a bomb similar to two used in the Boston Marathon bombings two years ago that killed three people and injured more than 260 others. He allegedly instructed someone how to fill the bomb with nails, metal and other items dipped in rat poison. Police base the charge on his communication of five web links to sites that provided instructions that could be used to make explosives as part of a plot to explode a bomb on September 13 at a memorial ceremony in Kansas City, commemorating the 9/11 terrorist attacks.”

Goldberg claimed, however, that he did not intend for an attack to take place. He said he wanted to inform police of the plan ahead of time in order to get credit for stopping an attack. He also said he thought the bomb-maker may kill himself in the process and at another point claimed that he did not expect anyone to actually build the bomb as “these guys are pussy keyboard warriors.”

The Herald reported that Goldberg is suspected of various other online hoaxes.

Australian Federal Police acting deputy commissioner for national security Neil Gaughan said Goldberg had presumed he was safe.

“This man thought that he could willingly and maliciously distribute disturbing information via the Internet and never have his identity discovered,” Gaughan said.

“This operation again highlights how law enforcement can investigate people in the online space and use our long-established partnerships to work with overseas agencies to bring people to account for their actions.”