District Attorney Jack Thorp announced Monday that Joshua Herrington, 23, reached a plea agreement in the death of Brennon Davis.
Herrington will serve a life sentence in the January 2011 death of Davis.
Wagoner County Sherriff's Office said Davis' body was found near the Jackson Bay area of Ft. Gibson Lake.
Deputies said neighbors heard gunshots and when they arrived, they found a body badly burned.
"This was a tragic and senseless murder, Thorp said. "Davis had his whole life ahead of him, but he got tangled up with two grown men that had no business hanging out with a high school student. Now, one of those men will pay for this for the rest of his life."
Harrington's co-defendant Cody Thompson's murder trial is set for October, Thorp said.