Mobile users can click here to see a slideshow of Matthew Leathers.
Leathers joined the military in 1998 and joined SEAL Delivery Vehicle Team One at Pearl Harbor in August of 2004.
While his friends said he was a fierce competitor on the trails, they add he was also someone with a lot of compassion for others.
"He would give you the shirt off his back. He was a good guy. He would do anything for you."
That is why Leather's friends said his disappearance has been so difficult, because they have been unable to anything for him.
"There's not enough good people in the world, and when you lose one of those good people, when someone like that goes -- it's hard."
Other endurance runners with H.U.R.T. said at their next race in April they will remember the impact Leathers had on their sport and their friendships.
They also hope to turn it into a fundraiser for Leathers' family.