The man who authorities say tried to carry out a mass shooting in Yellowstone National Park last year spewed racist views months before his attempted attack, prosecutors said in court documents.In documents filed with the U.S. District Court in Wyoming last week, federal prosecutors said Samson Fussner, 28, planned the potential mass shooting they called "a terror attack" and revealed his plans to his brother.Fussner ranted about his mental health issues, racist ideas and plans for mass shootings in the employee dining room and at a fireworks display in West Yellowstone, Montana, according to court documents.Prosecutors said in the documents that Fussner had a history of expressing white supremacist and antisemitic views and that he was an active member of a website dedicated to those views. Prosecutors filed the documents in an effort to have Fussner's weapons, ammunition, and SUV that were seized during the investigation forfeited to the government.Watch: Yellowstone National Park released bodycam footage of the July 4 shooting Yellowstone National Park releases bodycam footage of July 4 fatal shootingThe gunman revealed his plans to commit violence to his brother days before dying in a shootout with park rangers, according to court documents. He complained to his brother about Yellowstone in text messages, prosecutors said, using racial slurs to describe people there and calling the park a "hellscape," according to the documents. Fussner worked for a private business that was authorized to operate in Yellowstone, according to the National Park Service.Fussner had also texted his brother that he was obsessed with a woman at the park who he would later hold hostage before the shootout with park rangers, according to the documents.For about two hours on the night of July 3, Fussner, armed with a handgun and a knife, held the unidentified woman hostage in her dorm room after she told him she wasn't romantically interested in him, according to the documents.Fussner hid the gun just before midnight when the woman's roommate entered, according to the documents. When the roommate went to take a shower, he left, and the woman alerted security officers with the private business that employed Fussner.Law enforcement rangers with the park service swarmed the area around the dorm and the employee dining room, authorities said. Fussner opened fire after he was spotted walking out of a forested area on the morning of July Fourth, and the rangers returned fire.RELATED COVERAGE:Yellowstone National Park releases bodycam footage of July 4 fatal shootingOfficials say gunman at Yellowstone had plans to carry out July 4 mass shootingsXanterra issues statement following shooting in Yellowstone National ParkYellowstone Park ranger injured in shootout released from hospitalAuthorities identify man killed in shootout at Yellowstone National ParkCanyon Village shootout: Tourists react to fatal Yellowstone National Park incident on 4th of JulyRanger injured, suspect dead in shooting at Yellowstone National Park