The senior fell from the roof while installing a solar panel on top of the house in Ganterschwil, Saint Gallen cantonal police said.
He slipped on wet roof panels, slid down the roof, fell on scaffolding then plunged about three and a half metres onto a stone staircase, police said.
A Rega emergency rescue team flew him by helicopter to a nearby hospital for treatment of severe head injuries.
Meanwhile, an officer who climbed up to the roof to take pictures also slipped and fell onto the scaffolding before tumbling a further two metres into a field.
An ambulance crew transported the 49-year-old policeman to hospital for treatment of a torn tendon and multiple bruises, police said.