A Vape Pen, a Fall and a Question That Won’t Go Away: Why Did Nico Die?

It has been a year since Kathleen Kelley got the devastating call.

Her 17-year-old son, Nico, the youngest of her three children, had fallen six stories from the roof of their Manhattan apartment building and died.

Since then, she has pleaded with the police and Manhattan prosecutors for answers. She has asked her son’s friends and classmates at Fordham Preparatory School in the Bronx for any details about what happened on that rainy afternoon. And when an official investigation revealed scant information, she hired a private investigator.

To this day, Ms. Kelley, 58, has only one major clue about the final moments of her son, Nico Nuño-Kelley, who was supposed to start his first year at the University of Notre Dame last autumn. Minutes before he climbed to the roof of their Gramercy Park apartment in the driving rain on May 20, 2023, he inhaled marijuana from a friend’s vape pen and began acting erratically, according to statements the police and one of the two friends with him that afternoon gave to the private investigator.

The medical examiner’s office ruled Nico’s death an accident, but the uncertainty about what led to his fall has tormented his family. The friend who was said to have given him the vape pen has refused to talk to the police, to Ms. Kelley or to the investigator, and the police did not recover the pen.

A toxicology report, which relied on blood samples taken from Nico after his death, revealed high levels of THC — the chemical responsible for most of marijuana’s psychological effects — in his system. But the drug, according to specialists who have studied the effects of marijuana on the brain, rarely leads to the kind of reckless impulse that apparently led Nico to go up to the roof.

Ms. Kelley, a commodities adviser who owns her own company, said she fears she and her ex-husband, Hilario Nuño, Nico’s father, will never know the full truth about their son’s death.