Kim Wall has almost given up on hearing from Peter Madsen.

Madsen was something of a local celebrity-inventor in his native Denmark, his exploits often featured in magazine profiles and on television, where his arrogant personality fascinated the reticent Scandinavians. He had recently fallen out with some of his fellow rocket enthusiasts, this time over the building of a spaceship that he planned to pilot. Wall, an impressively credentialed 30-year-old journalist, wanted to interview the 46-year-old self-styled “inventrepreneur” for a freelance article about his efforts and his growing rivalry with other amateur rocket builders in Copenhagen. But Madsen was proving a difficult get.