The U.S. Coast Guard officer accused of planning a widespread terrorist attack on politicians and media personalities in the Washington area conducted Internet searches for the best gun to kill black people and the home addresses of two Supreme Court justices before going to firearms sales websites, prosecutors asserted in new court documents.

The fresh allegations come in a motion that government officials filed Tuesday as they prepare to argue that Lt. Christopher P. Hasson, 49, should remain in jail pending trial. Hasson is set to appear in federal court in Greenbelt, Md.,, Md., on Thursday for a review of his detention status.

Hasson, of Silver Spring, has been charged with drug and weapons offenses but no ­terrorism-related counts. He has entered a plea of not guilty.

His federal public defender has argued that the government has no proof Hasson intended to launch an attack and that it would be inappropriate to keep him in jail on drug and weapons charges.

Federal prosecutors with the U.S. attorney’s office say in recent court filings that Hasson “continues to pose a serious danger.” Prosecutors also argued that one of the weapons counts involving the suspected illegal possession of silencers reflects what they say is a plot for destruction by a self-professed neo-Nazi.

“The silencers serve one purpose: to murder quietly,” Assistant U.S. Attorney Thomas Windom wrote in a motion saying that Hasson should remain detained. “The defendant intended to do so on a mass scale, and his detention has thwarted his unlawful desire.”

Hasson’s federal public defender declined to comment Tuesday, but in Hasson’s first detention hearing, his attorney at the time called the government’s accusations “inflammatory” without evidence of a plot.

The new motion does not name the Supreme Court justices in Hasson’s alleged Internet searches in March 2018 but says that he had also searched for their home addresses along with the addresses of two social media executives minutes before going to sites that sell firearms. Hasson had also searched for “best n----- killing gun” before going to the weapons sales sites, prosecutors said.

“The defendant’s Internet search history lays bare his views on race, which in turn inform his criminal conduct,” Windom wrote in a footnote to his motion. The footnote said Hasson searched for “white homeland,” “when are whites going to wake up,” and “please god let there be a race war” in 2017.

Hasson has been charged with illegal possession of unregistered and unmarked silencers, illegal possession of firearms by an unlawful user or addict of controlled substances, and simple possession of a controlled substance.

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

Prosecutors allege Hasson had been amassing weapons for an attack since at least 2009, buying weapons from California and Virginia. Hasson purchased parts for silencers in July 2017 and used a drill press later found in his home during a search warrant, to assemble the silencer of “clandestine manufacture,” prosecutors allege in court documents.

Prosecutors also outlined what they said was Hasson’s history of associating with neo-Nazis and “skinheads” as reasons he should remain jailed.

Prosecutors again pointed to a draft letter Hasson wrote in September 2017 to a “known American neo-Nazi leader” supporting a “white homeland.” In the court filings, prosecutors say Hasson was present when a person they say is a neo-Nazi leader, referred to by a nickname in the court filing, attempted to shoot a man in 1995. After the gun did not fire, the alleged neo-Nazi leader — wearing a black jacket with swastika patches — assaulted the man with Hasson present, prosecutors wrote. Prosecutors said the neo-Nazi leader was convicted and sentenced but did not indicate whether Hasson was charged in the same incident.

Hasson and the leader appeared to remain in touch through a relative after the FBI interviewed the leader in March the court filing from the government said . Hasson cursed when he learned the FBI had interviewed the leader, prosecutors said.

The government alleges Hasson used his government computer to study the manifestos of terrorists, paying particular attention to the writings of the right-wing Norwegian terrorist who killed 77 people in 2011.

“It cannot go unnoticed that the terrorist who perpetrated the New Zealand attacks in March 2019 was a devotee of far-right Norwegian domestic terrorist Anders Breivik — from whom, as discussed in the Motion for Detention, the defendant also took criminal direction,” Windom wrote in the motion.