A 13-year-old Oklahoma boy has been charged as an adult in the 2017 crossbow killing of another boy, age 10.

Shane Edward Brooks has been charged with first-degree murder for allegedly killing 10-year-old Austin Almanza with a crossbow, the Oklahoman reported Thursday. Brooks reportedly investigators he was hunting when he "accidentally shot" Austin and his younger brother, 8-year-old Ayden Almanza. Ayden, however, told authorities that Brooks was "mad at them."

"Shane was careless with the crossbow," Roger Conway, the Almanza brothers' uncle, told investigators of the Oct. 21 incident. Lincoln County authorities determined both brothers were reportedly struck with a single bolt, which traveled through Austin before hitting Ayden in the left arm. Austin's death was later found to be the result of a crossbow bolt wound to his abdomen. Though Brooks was arrested the same day the shooting occurred, his name was initially withheld.

Ayden told authorities that Brooks (who he described as "always mean") was angered by his and Austin’s decision to leave, at which point Brooks allegedly "jumped down" from a tree and hid behind tall grass with the crossbow. A hunting arrow was then shot from the camouflage crossbow with an attached scope. Brooks is also believed to have had access to "multiple weapons" including pistols and a rifle. Previously, investigators said, Brooks had shot Ayden using airsoft guns.

Brooks, who was released on bail under strict conditions in December, has now been ordered to undergo a psychological evaluation. His next scheduled court appearance is Feb. 1.