Updated

A 13-year-old Oklahoma old boy admitted to killing his older brother in March and setting the body on fire, authorities said this week. 

The boy confessed to the slaying of his 16-year-old brother during a follow-up investigation, The Express-Star reported, citing the Grady County Sheriff's Office. He is charged as an adult with first-degree murder and desecration of a human corpse and arson. 

Deputies were called to a house fire in Bridge Creek, located 27 miles south of Oklahoma City, on March 6 where a body was discovered with an air compressor hose wrapped around the neck of the victim. 

A 21-year-old man at the home told authorities he was playing a computer game when the fire alarms went off. He said his younger brother, the 13-year-old, told him the fire was in the garage. When the older brother went to the garage, he found the victim lying next to a wheelbarrow, which was on fire. 

On Monday, Investigators spoke with the boy, 13, and his mother.

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During a second interview, the boy admitted to the killing, KOCO-TV reported. He allegedly placed a pillowcase over the head of his brother and choked him until he passed out. He allegedly told investigators he used the air compressor hose to "finish off" his brother, according to KWTV-DT.

He said the two had planned out his brother's death as an assisted suicide a month before the incident. Their mother was out of town with another one of their siblings at the time. 

The boy is being held in Grady County jail on a $500,000 bond. Fox News has reached out to the sheriff's office but has not heard back.