The charges against a Coast Guard lieutenant who investigators said espoused white nationalist views and compiled a hit list of prominent Democratic politicians and media personalities do not warrant keeping him in custody before trial, a federal magistrate ruled Thursday.

U.S. Magistrate Judge Charles Day ordered a follow-up detention hearing at which Christopher Hasson's defense team will be required to propose suitable release conditions. The judge noted that he had "grave concerns" about Hasson and warned that he would "have to have a whole lot of supervision." Federal prosecutors said late Thursday that they will challenge any release conditions sought by Hasson's defense team in an effort to keep him in custody pending trial.

"As of now, Mr. Hasson remains detained pending further possible proceedings," U.S. Attorney's Office spokesperson Marcy Murphy said in a statement, adding: "If Judge Day does order the defendant’s release, the Government intends to appeal such release to the U.S. District Judge presiding over the case, on the basis of the danger to the community posed by the defendant."

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Hasson, 50, was arrested Feb. 15 in the parking garage of the Coast Guard's Washington headquarters. He has pleaded not guilty to charges of unlawful possession of silencers, possession of firearms by a drug addict and unlawful user, and for possession of the opioid painkiller tramadol.

Following a bail hearing days after Hasson's arrest, Day agreed to keep the defendant held in custody but said he was willing to revisit his decision if prosecutors didn't bring more serious charges within two weeks. Hasson's attorney, Liz Oyer, wrote in a court filing last week that prosecutors recently disclosed they didn't expect to seek any additional charges.

Prosecutors described Hasson in court documents as a "domestic terrorist" who "intends to murder innocent civilians on a scale rarely seen in this country." According to a court filing, Hasson compiled a spreadsheet of so-called "traitors" that he subdivided into three categories: A,B, and C. So-called "Category A" traitors included Democratic Sens. Chuck Schumer of New York, Tim Kaine of Virginia, Richard Blumenthal of Connecticut (labeled "Sen blumen jew" in the spreadsheet), Elizabeth Warren of Massachusetts (labeled "poca warren"), Kirsten Gillibrand of New York, Cory Booker of New Jersey and Kamala Harris of California.

Also listed in "Category A" were House Speaker Nancy Pelosi, D-Calif., Rep. Alexandria Ocasio-Cortez, D-N.Y., Rep. Maxine Waters, D-Calif., MSNBC personalities Joe Scarborough, Chris Hayes and Ari Melber as well as CNN host Don Lemon. Names in the "Category B" list included Rep. Ilhan Omar, D-Minn., CNN personalities Chris Cuomo and Van Jones and the Democratic Socialists of America.

At a bond hearing in February, prosecutor Jennifer Sykes said Hasson also would log on to his government computer during work and spend hours searching for information on such people as the Unabomber, the Virginia Tech gunman and anti-abortion bomber Eric Rudolph. Hasson also allegedly Googled topics including "most liberal senators," "best place in dc to see congress people," and "civil war if trump impeached."

Prosecutors' motion for pre-trial detention also included extracts from draft emails in which Hasson wrote he was "dreaming of a way to kill almost every last person on the earth." In a separate draft letter to a neo-Nazi leader, prosecutors said Hasson "identified himself as a White Nationalist for over 30 years and advocated for 'focused violence' in order to establish a white homeland."

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Investigators also found and removed 15 guns, including seven rifles, and over 1,000 rounds of ammunition from Hasson's basement apartment in Silver Spring, Md., prosecutors said.

Hasson faces up to 31 years in prison if convicted on all charges. No trial date has been set.

Fox News' Bill Mears and The Associated Press contributed to this report.