After a drizzly hike through one of Japan’s lush mountain ranges earlier this year, Luigi Mangione, a computer engineer in his mid-20s who had set off on a long solo trip to Asia, paused to record a voice message to a friend he had met while traveling abroad.
Making his way that day along a river gorge in the Nara region, Mr. Mangione had fled his day-to-day life in Hawaii to soak in hot springs, meditate, catch up on books and do some writing of his own.
“I want some time to Zen out,” Mr. Mangione said in the recorded message on April 27, his voice quiet and contemplative.
It would be one of his last communications before he abruptly cut ties with a wide range of friends and family, who eventually set out on a desperate hunt to track him down. Seven months later, Mr. Mangione emerged from his isolation as the suspect in the brazen assassination of Brian Thompson, the chief executive of UnitedHealthcare, on a sidewalk in Manhattan.
Police investigators have been scrambling to trace Mr. Mangione’s movements not only in the days before the Dec. 4 shooting, but also in the months that preceded it — a period that has been shrouded in mystery.
But in new records and messages reviewed by The New York Times, along with interviews with a wide range of people who knew Mr. Mangione, a more complete picture has emerged of a young man struggling with debilitating medical problems and increasingly disillusioned with the society he lived in.
