YA, non-fiction, about a Father and a Child trying to survive stranded in a forest. **Spoilers Ahead**

[Isaac]

A non-fiction book about a father and son trying to survive alone in some sort of beach/island, they mention another character but never show him/her. The father is old and has to stay in the shore (in their camp area), and the son goes hunting by himself with a rifle. The dad warns him about the traps and wires that were set in the forest he was going to.
I remember he was mentioned to climb up a hill of rocks and him slowly disappearing from the father's sight, after this, you hear some shots, and when the dad goes into the forest to find the son, he "finds" him and comes back with him, except it wasn't him, but an image made by his mind in order to not go insane.
The last image is him walking away from the forest with his "son", and then the author describing that he was walking away from a bunch of wires that had his dead son stuck in the wires, who probably shot himself when he fell in the wires.

I read this about 2015 in my freshman English class (in high school) (Austin Tx District)

[Rainbowheart]

Are you sure this was non-fiction?

Do you remember how the man and his son wound up on the island? Why were there traps and wires, were they left over from a war?