かと思うと describes a second event that happens immediately after the first, often so quickly that the speaker presents the change as surprising or unexpected. It commonly follows a verb in the plain past form and is used for sudden changes, repeated actions, or situations in which one state gives way to another. The subject may stay the same or change, but the two events are normally closely connected in time. The sentence after かと思うと is usually not a deliberate action planned by the subject.