The driver, a 42-year-old female ambulance technician, and the patient, an 88-year-old man, were pronounced dead at the scene.
A male crew member and a male relative of the patient remain in hospital both in a serious condition.
More top news
Wednesday morning's weather for the west of the region
Wednesday morning's weather for the east of the region
A school in Sussex has been chosen to pilot a new type of 'first aid' training for children's mental health