4 peices of evidence

When the normal school year starts in September, Brinker has moved into Leper's old room across the hall from Gene and Finny. He comes into Gene's room and makes a joking accusation that Gene caused Finny's accident in order to get the room all to himself. Brinker goes down to the Butt Room with Finny where the gag continues.

Brinker makes fun of Leper for being a naturalist.

One day he takes Gene aside and again brings up his suspicions concerning Finny's accident.He finally comes to Gene and Finny's room, along with an entourage, and takes the boys after hours to the assembly hall, where about ten senior boys are waiting. This is Brinker's idea of a court martial.

After Finny's death, Brinker introduces his father to Gene, which explains a lot more about his motivations and anger.