Christopher Paul Hasson worked at the Coast Guard’s headquarters in Washington and had allegedly expressed extremist views for several years.
Court papers detail a June 2017 draft email in which Mr Hasson wrote that he was "dreaming of a way to kill almost every last person on the earth," and pondering how he might be able to acquire anthrax and toxins to create botulism or a deadly influenza.
In the same email, he described an "interesting idea" that included "biological attacks followed by attack on food supply" as well as a bombing and sniper attacks, according to court documents filed by prosecutors.
When authorities searched Mr Hasson’s basement in Maryland they found 15 weapons – including several rifles – and over 1,000 rounds of ammunition.
They also found a container with more than 30 bottles that were labelled as human growth hormone, court papers said.
Prosecutors have described him as a “domestic terrorist” and he will appear in federal court in Maryland on 21 February.
"The defendant is a domestic terrorist, bent on committing acts dangerous to human life that are intended to affect governmental conduct," prosecutors wrote in court papers .
In September 2017, Mr Hasson sent himself a draft letter that he had written to a neo-Nazi leader and "identified himself as a White Nationalist for over 30 years and advocated for 'focused violence' in order to establish a white homeland," prosecutors wrote.
He routinely read portions of a manifesto written by Norwegian mass murderer Anders Behring Breivik that prosecutors said instructs would-be assailants to collect firearms, food, disguises and survival tools, court papers said.
Mr Hasson has also expressed admiration for Russia and prosecutors say during the past two years he has regularly searched online for pro-Russian as well as neo-Nazi literature.
Prosecutors allege Mr Hasson visited thousands of websites that sold guns and researched military tactical manuals on improvised munitions.
Mr Hasson "began the process of targeting specific victims," including several prominent Democrats in Congress and 2020 presidential candidates.
His list of prominent Democrats included Nancy Pelosi, Chuck Schumer and presidential hopefuls Kirsten Gillibrand, Elizabeth Warren, Cory Booker and Kamala Harris.
The list – created in a Microsoft Excel spreadsheet – also included mentions of John Podesta, who was Hillary Clinton's campaign chairman, along with Beto O'Rourke, Alexandria Ocasio-Cortez and Maxine Waters, MSNBC's Chris Hayes and Joe Scarborough and CNN's Chris Cuomo and Van Jones, according to the court filing.
He was arrested on gun and drug offences, but prosecutors say those charges are the "proverbial tip of the iceberg."
Mr Hasson appeared to be a chronic user of the opioid painkiller Tramadol and had purchased a flask filled with four ounces of "synthetic urine" online, prosecutors said.
Authorities suspect Mr Hasson had purchased fake urine to use in case he was randomly selected for a drug test.
The chief at the federal defender's office in Maryland – which is representing Mr Hasson – declined to comment on the allegations.
The Coast Guard did not immediately respond to a request for comment on Mr Hasson's arrest.
Additional reporting from agencies
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