BOULDER, Colo. (AP/WCCO) — Authorities have released the name of a Minnesota teen who died in a Colorado hiking accident.

The Boulder County coroner said 17-year-old Carter Christensen of Maple Grove, Minnesota, died in a fall on Sunday evening in Cahutauqua Park near Boulder, which is just northwest of Denver.

(credit: Christensen family)

The sheriff’s office says Christensen was climbing alone without the use of ropes or gear when he fell, possibly more than 100 feet (30 meters), suffering “massive traumatic injuries.”

Investigators say nobody witnessed the fall, but several people in the area heard it and responded to help.

Christensen posted a selfie from his climb on social media about an hour before he fell. His family released the photo.

Christensen’s family said he had just graduated from high school, was visiting friends in Colorado and planned to enlist in the Navy.

His older brother, Hayden Christensen, gave this statement to WCCO Wednesday evening:

No mere words can do justice to describe the character my brother had. He was fearless in every aspect of life and the bravest person I have ever known.

He was my younger brother but taught me what it meant to live life to the fullest. He was doing what he loved most, knowing that eases my mind a bit in this time of intense pain.

He was my sidekick in life, and was always there for me. He will be deeply missed by all those who got the chance to know him.

(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)