Two brothers in the United States have been charged with murder after they allegedly kicked a 16-year-old boy 100 times and repeatedly struck his head with a rock during a camping trip.

The pair then allegedly buried his heavily beaten body in a grave but, afraid it would be discovered, they dug it up and reburied it.

Moments before the brutal killing, Jonathon Adamson, 21, and Benito Marquez, 16, told Lewis County Superior Court they sexually assaulted Benjamin Eastman with a stick.

The pair were charged on Monday with murder, rape, tampering with physical evidence and unlawful disposal of remains after Eastman’s body was found in a shallow grave last week.

Prosecutors decided to charge Marquez as an adult due to the brutality of the attack.

The judge ordered their bail be set at US$10 million.

According to court documents, the brothers lured Eastman into the woods for a camping trip in the early hours of June 24, where they planned to assault him.

Adamson allegedly told detectives that once they were in the woods, they proceeded to get Eastman on the ground and assaulted him for between 20 and 45 minutes.

Adamson said he estimated they kicked Eastman more than 100 times. A pathologist agreed with those numbers and said the boy died of blunt-force trauma.

Adamson also told detectives they sexually assaulted Eastman with a stick while he was still alive.

The brothers then allegedly hit Eastman repeatedly in the head with a rock to make sure he was dead, then buried him and burned his clothes, their own clothes and the shovel they used to dig the grave.

They began to worry the burial site would be discovered, so they soon dug him back up and buried him in another place, this time marking the grave with a cross made out of sticks.