Friends of avid trail runner Alex Nunn are grief-stricken after hikers found his body in Tantalus.

“He was just the nicest, kindest, gentlest man with the biggest smile,” said John Salmonson, founder of the Hawaiian Ultra Running Team (HURT).

Honolulu police are investigating the death of a man identified by friends as Nunn, 33. Hikers on Pu‘u Ohia Trail found him unresponsive near 4050 Tantalus Drive on Saturday afternoon.

Police said there are suspicious circumstances surrounding his death but declined to comment further due to the ongoing investigation. The case is classified as an unattended death.

Nunn, originally from Southern California, moved to Honolulu almost 12 years ago. He enjoyed trail running and participated in the grueling HURT 100-mile race in Tantalus that consists of five 20-mile loops.

The race, Salmonson said, is considered one of if not the hardest trail races in the country because of its rugged terrain.

Nunn placed third in the race in 2014 and second place the following year. “He was very, very athletic and fast,” Salmonson added.

He also participated in the 2,650-mile Pacific Crest Trail where he hiked for four months from Mexico to Canada.

Friend Kim Baxter, who knew Nunn for 10 years, described him as a spectacular runner with an adventurous spirit. “Everybody loved him. He was so kind and thoughtful,” she said.

Baxter said a friend informed her of Nunn’s death Sunday morning. “It took a while to sink in. It’s still obviously very raw.”

Friends said Nunn will be best remembered for his kindness and smile. “He was the nicest guy in the world,” Salmonson said.

A memorial in remembrance of Nunn is scheduled to be held at the volleyball court at Fort DeRussy Beach Park at 5 p.m. April 14.

A GoFundMe account also has been created to assist Nunn’s family with expenses. Those interested in making a donation can visit 808ne.ws/alexnunn.