ORANGE PARK, Fla.   — The person behind the online moniker “Australi Witness” claimed to be an Australia-based radical with ties to ISIS who was using the Internet to nurture terror plots around the world, authorities say. He peppered his messages to an FBI informant with “kuffar,” a derogatory term for non-Muslims, and said he was consulting with other jihadis to help the person plan a bombing in Missouri on the 9/11 anniversary.

But in reality, investigators and neighbors say, Joshua Ryne Goldberg was a reclusive 20-year-old who rarely left his room at his parents’ house in a quiet neighborhood of retirees in the Jacksonville area. From there, he posted his boasts on a site frequented by ISIS supporters, but also confided in an online acquaintance that he was an “online troll” who liked to stir up trouble through hoaxes, according to a criminal complaint.

This week, Goldberg was arrested and charged with distributing information relating to explosives, destructive devices and weapons of mass destruction. The complaint says Goldberg told the informant how to build a bomb and suggested the informant target a commemoration of the Sept. 11, 2001 attacks in Kansas City. No bomb was produced.

Goldberg caught the attention of authorities after online posts calling for an attack on the May 3 contest for drawings of the Prophet Muhammad in Garland, Texas. A federal agent wrote that a message attributed to “Australi Witness” was retweeted by one of the two armed gunmen on the morning of the attack.

The suspect later boasted on a site used by ISIS supporters that he was also helping gunmen plan attacks on synagogues in Melbourne, Australia, and Los Angeles, the complaint says. Investigators in those cities determined there wasn’t a threat, but Australian authorities plan to charge him there.

Identifying himself as a Lebanese refugee living in Australia, he wrote: “I have dedicated my life to striking fear into the hearts of the kuffar and coordinating attacks of jihad around the world,” according to the complaint.

Earlier this year, federal investigators traced online messages associated with “Australi Witness” to an account in Orange Park, about 15 miles south of Jacksonville, according to the complaint.

In July, an informant directed by the FBI began exchanging messages with the suspect, with the informant eventually suggesting it was time “put some more irons in the fire bro.”

On Aug. 20, according to the complaint, Goldberg asked the informant what kind of attack he wanted to carry out. “I was thinking a bombing,” Goldberg states, according to the complaint. The informant, who claimed to be a student living near Kansas City, concurred.

Goldberg said a pressure cooker bomb would work best and suggested attacking the Kansas City event, according to the messages. Authorities say Goldberg sent bomb-making instructions and told the informant to dip screws and other shrapnel in rat poison.

The complaint quotes the suspect as telling the informant: “Get FAR away from the bomb, brother. There’s going to be chaos when it goes off. Shrapnel, blood and panicking ...”

Attorneys appointed to represent Goldberg didn’t respond to email messages. A judge set a Tuesday bail hearing for him.

Australian police told the FBI that they interviewed a witness who exchanged messages with Goldberg. The witness said the suspect was an “online troll” and “proponent of radical free speech” who liked to stir up trouble through hoaxes, according to the complaint.  

In a May conversation quoted by Australian police, the witness asked Goldberg if he was worried an extremist might kill at his behest, to which he responded he was corresponding with cowardly “keyboard warriors.”