Why does brother leave doodle in the rain?

Brother leaves Doodle in the rain out of frustration and a desire to assert his independence. He feels burdened by Doodle's physical limitations and wants to distance himself from the responsibility of caring for him. This moment underscores the themes of pride and guilt, as Brother's actions reflect both his internal conflict and the pressure he feels to conform to societal expectations of masculinity and strength. Ultimately, this decision has tragic consequences for their relationship.