At two points of the reference frame K two events occurred separated by a time interval t. Demonstrate that if these events obey the cause-and-effect

At two points of the reference frame K two events occurred separated by a time interval Δt. Demonstrate that if these events obey the cause-and-effect relationship in the frame K (e.g. a shot fired and a bullet hitting a target}, they obey that relationship in any other inertial reference frame K'.