Policeman kidnapper and manhunt

So hi I don’t remember a movie
It’s an American thriller, it’s about a teenager who thinks his neighbor is a kidnapper and investigates him, no one believes him because his neighbor is a family friend and also a policeman, the teenager goes into his neighbor’s house and discovers in the basement a child in a bathtub, everyone discovers that he was right but the neighbor disappears , during the night he leaves the attic, kidnaps the 2 children and takes them in a forest for a manhunt
One of them get killed by the neighbor and the other one is left in the woods and someone who pass by finds him.
I remember a lot of details like when he got to the basement he was filming with an old camera, or he find a lot of chemicals products that he’s neighbor bought and we saw after that it was for planting trees in the city, that one time he saw by the window his neighbor with blood on him, in the backyard of his neighbor there where suspicious disturb dirt but it was only plantations.
Okay I hope someone help me because I search everywhere I can’t find it :weary:

Quite sure it’s, “Summer of 84” 2018

I love this Movie! ;o)