During the sexual assaults King would say: "This won't take long."
Court documents also revealed that the second girl, who was violated by King in a similar way, heard during one attack "a clicking noise like the sound of a camera shutter".
The girl recalled seeing King then place his cellphone in a pouch on his belt.
During King's trial last month an expert witness discovered the "digital footprints" of two videos on the ambulance officer's cellphone after he sexually assaulted and made intimate recordings of a 15-year-old female patient.
Police found King had used his Samsung Galaxy S3 to record the teen while he stopped the ambulance on the side of the road near Waipawa, while transporting the girl to a medical centre in Waipukurau.
A second video was also created on King's phone outside the medical centre just minutes before the teenager fled from the rear of the ambulance and burst through the front doors of the centre to the astonishment of medical staff.
King was remanded in custody and will be sentenced for all matters on December 18.