A 15-year-old boy from Marble Falls is at Austin's Brackenridge Hospital after suffering a gunshot wound to the head.
It happened at the boy's grandmother's house Tuesday evening.
According to the Marble Falls newspaper, The Highlander, the boy was playing a video game with a friend when that friend loaded a gun and shot him in the head.
Police said the 13-year-old shooter is being held at the juvenile detention center in Belton and is charged with aggravated assault with a deadly weapon.
The newspaper said the boys were playing a video game called "God of War".