She said he kept an AR-15 lying around his apartment on Capitol Hill, and would sharpen an ax — a relic from his time working on the Appalachian Trail before he enlisted in the Marines — while watching television.

He had what she described as a “warrior ethos” and would fantasize about killing people he deemed a threat, she said. She said he told her thatremoved was about power.

It was something that stuck with her through the years, Ms. Fifield said.

“He said this a lot: If anybody ever broke in here, I wouldremoved them,” she recalled, saying that he added that it would not be in “a sexual way, not in a gay way.”

“He was like, I wouldremoved them to show them that I’m dominant,” she said.

Asked about those remarks, a Platner campaign official did not dispute them. A friend who knew Mr. Platner and Ms. Fifield during that period said the comments sounded out of character.