The body of 25-year-old Joshua R. Schenk, of Vancouver, was discovered Friday by a hiker.
The victim's roommate, Matthew E. Starr, 19, was interviewed later in the day and subsequently booked into the Clark County Jail on one count of first-degree murder.
According to court documents, Starr told police he was target shooting with Schenk and slipped while walking, then accidentally pulled the trigger and shot Schenk in the back of the head.
The court documents said that Starr told investigators he felt Schenk may be suffering and knew that emergency help was more than five minutes away, so he shot Schenk again, this time intentionally.
"Starr said he shot his friend the second time to put his friend out of his misery," the probable cause document stated, "...like you would a deer."
Then, police said Starr and his friend, Zachary Mattson moved Schenk's body about five feet away and covered it with a tarp.
Police said Starr also took $300 from Schenk's wallet before leaving.
Starr was arraigned in court Monday and his bail was set at $1 million.
Police said he had one pound of marijuana in his possession when he was arrested.