A federal judge is expected to release a U.S. Coast Guard lieutenant accused of plotting an attack on politicians and journalists pending trial on gun and drug charges because prosecutors have not charged him with terrorism-related offenses.

U.S. District Judge Charles B. Day said he had “grave concerns” about Christopher Hasson, 50, of Silver Spring, Md., during a detention hearing Thursday in Greenbelt, Md., but could not justify holding him without more serious charges.

Day said he will hold a hearing in the coming days to work out a suitable supervision arrangement for Hasson that will include electronic monitoring and other measures before releasing him.

While noting the difficulty federal law enforcement faced with the disturbing evidence about Hasson, Day said flatly, “I do not find detention appropriate.”

Federal prosecutors have argued in court documents that Hasson planned to “murder innocent civilians on a scale rarely seen in this country,” amassing an arsenal of guns and typing up a list of targets that included House Speaker Nancy Pelosi and MSNBC host Joe Scarborough. He also researched unidentified Supreme Court justices.

“He was planning a strike. He was going to strike when ready,” Assistant U.S. Attorney Thomas P. Windom said in arguing against Hasson’s release. “We’re not telling you that. It’s the defendant telling you. That is his own writing.”

Windom did not explain in court why prosecutors had not brought more serious charges against Hasson if they believe he aimed to carry out an act of domestic terrorism. Hasson has been charged with illegal possession of unregistered and unmarked silencers, illegal possession of 15 firearms by an unlawful user or addict of controlled substances, and simple possession of a controlled substance. He was arrested in February and has pleaded not guilty.

Hasson’s case poses a challenge for the government, which is working within federal statutes that define terrorism involving international organizations but do not do the same for domestic terrorism suspects.

Most people the FBI arrested in domestic terrorism investigations are charged with drug, weapons or other non-terrorism-related charges, according to a review of internal FBI figures by The Washington Post.

After Thursday’s hearing, the U.S. attorney’s office for Maryland said in a statement that the government “will oppose any conditions of release. 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.”

Assistant Federal Public Defender Liz Oyer vigorously disputed prosecutors’ characterization of Hasson, saying they offered no concrete evidence of when, how and where they believe her client was planning to strike. She said he has served honorably in the military for 30 years and called his writings private thoughts, not a plan for mass killing. She indicated prosecutors had told her they ruled out filing terrorism-related charges against Hasson.

“I feel that the vivid imagination and colorful writings of prosecutors have developed a profile for this case it doesn’t deserve,” Oyer told Day.

Oyer said the failure to bring more serious charges was striking because federal law enforcement officials had conducted a thorough, months-long investigation of Hasson. She said they set up video surveillance on Hasson’s home and desk at U.S. Coast Guard headquarters in Washington, searched his residence, tracked his car, examined the contents of his phone and talked to past acquaintances among other avenues of inquiry.

Oyer said Hasson was prepared to submit to electronic monitoring and supervision by family members in Arizona if released, but Day said he wanted more time to work out an arrangement locally. A follow-up hearing was not immediately scheduled.

“We have got to have someone who has eyes and ears on him like nobody’s business,” Day said of Hasson.

Hasson was arrested in February after a computer program the Coast Guard uses to flag insider threats alerted authorities about suspicious activity, federal authorities have said.

Coast Guard officials said Hasson no longer works at the Washington headquarters, where he had been stationed since 2016. Hasson also served in the U.S. Marine Corps from 1988 to 1993 and in the Army National Guard for roughly two years in the mid-1990s, according to court records.

Authorities assert that in uncovered writings, Hasson advocated for “focused violence” to “establish a white homeland” and said, “I am dreaming of a way to kill almost every last person on the earth,” according to court records. In court Thursday, Windom said Hasson had been a skinhead for decades.

Government officials said he had been amassing supplies and weapons since at least 2009. Prosecutors also said Hasson had been studying the manifesto of Anders Breivik, the far-right terrorist who killed 77 in twin attacks in Norway in 2011. Breivik took narcotics and steroids as part of his preparations.

A law enforcement raid of Hasson’s small basement apartment found a locked container with more than 30 vials of what appeared to be human growth hormone, prosecutors said. Hasson had also ordered more than 4,200 pills of the narcotic Tramadol, along with synthetic urine to pass random drug screenings at work, court records show.

In Hasson’s case, the allegations of a terrorist plot did not emerge in the charges filed against him but in a later detention memo from prosecutors arguing he remain in jail. Prosecutors said Hasson is a self-professed white nationalist.

In new court filings this week, federal prosecutors say Hasson “continues to pose a serious danger.” The government alleged that Hasson visited firearms sales websites after conducting Internet searches for the “best” gun to kill black people and the home addresses of two Supreme Court justices.

Prosecutors also said Hasson purchased silencers with a single purpose — “to murder quietly.”

They also outlined in court records Hasson’s alleged history of associating with neo-Nazis and skinheads. Federal prosecutors said Hasson wrote to an American neo-Nazi leader in September 2017 saying he supported a “white homeland.”

Hasson was also present when the same leader attempted to a shoot a man in 1995, but the gun failed to fire, according to court documents. The leader then assaulted the man with Hasson nearby, filings in Hasson’s case assert. Federal prosecutors said the neo-Nazi leader was convicted in connection with the incident, but Hasson was not charged in that case.

Seamus Hughes, deputy director of the Program on Extremism at George Washington University, said federal law handcuffs prosecutors in domestic terrorism cases.

“The ‘material support for terrorism’ clause offers little flexibility for cases not involving foreign terrorist groups like ISIS,” Hughes said. “There isn’t a designated domestic terrorists list. As a result, the U.S. attorney’s office is restricted in what criminal offenses they can bring. This case is a perfect example of the gray area of terrorism charges and shows the limitations of current policies.”

Maryland federal defense attorney William C. Brennan said it is difficult to justify keeping Hasson incarcerated if he has only been charged on gun and drug offenses. Brennan said the law requires the “least restrictive combination of conditions” that will assure both the appearance of the defendant in court and the safety of the community.

“You can’t keep someone incarcerated for their beliefs as opposed to their charged conduct,” Brennan said. “They have to really look at what the person is charged with versus the rumor and innuendo.”

Brennan said pretrial supervision can be very intensive if the judge orders, including daily check-ins and GPS monitoring.

Hasson’s wife was in court Thursday but declined to comment after the hearing. Oyer said her client had no criminal record before his arrest on the recent charges.