A 20-year-old Florida internet troll who lived with his parents while masquerading online as the Perth jihadist "Australi Witness" attempted to organise a terror attack in Melbourne, according to authorities.  Joshua Ryne Goldberg has been arrested and charged with distributing information relating to explosives, destructive devices and weapons of mass destruction.  Disturbing details of Goldberg's alleged online exploits are contained in a criminal complaint filed in the US District Court.  It's alleged last month he encouraged a man he thought was a terrorist, but was actually a confidential FBI source, to make a pressure cooker bomb and detonate it in a crowd at a Kansas City 9/11 ceremony this weekend.  The event would be attended by firefighters and Goldberg allegedly encouraged the FBI source to use nails, glass and metal dipped in rat poison "because it increases the chances of killing those impacted".  Goldberg, according to the complaint, appeared to be fixated on Australia despite living half a world away in Florida.  During a direct message conversation, the FBI source allegedly asked Goldberg: "Why Australia bro? Just curious. Are they as bad as the US?"  "And yes, Australia is bad as the US," Goldberg allegedly replied.  Goldberg in July allegedly told the FBI source: "Right now, I'm trying to get a mujahid in Melbourne to carry out jihad, but he keeps delaying it."  "He has a gun already, but he insists on making a video message to the kuffar with a black shahada flag," the Florida man wrote.  "He also insists on getting his friend to carry out jihad with him. I am afraid he'll get caught before he can do it."  On August 5, Goldberg allegedly told the FBI source he feared the Melbourne man, who he originally met on Twitter, had been arrested.  Goldberg said he would be responsible for the arrest because he had posted about his Melbourne contact on a "muhajideen" discussion board, according to the complaint.  Goldberg also allegedly took responsibility for encouraging two armed men to attack a Muhammad drawing contest in Texas in May.  Australian Federal Police on Friday afternoon confirmed they helped the FBI track down the 20-year-old man.  They alleged Goldberg "provided information over the internet in an attempt to facilitate and encourage terrorist acts in Australia".  Australian authorities said US investigators took over when it was determined the person responsible for the threats was likely in the United States.  AFP acting deputy commissioner for national security Neil Gaughan said the alleged assailant had presumed he was safe.  "This man thought he could willingly and maliciously distribute disturbing information via the internet and never have his identity discovered," Acting Deputy Commissioner Gaughan said in a statement.  "This operation again highlights how law enforcement can investigate people in the online space."  Do you have any news photos or videos?
Authorities allege that Joshua Ryne Goldberg, who claimed online to be living in Perth, was actually plotting terror attacks from his home in Florida.