It looked to have been an unscheduled arrival with flight tracking websites suggesting that the Challenger 'diverted' into Rockhampton Airport while on a flight from Townsville to Brisbane.
Indeed after some time on the ground, VH-OFC "Ambulance 634" departed Rockhampton Airport and continued to Brisbane.
Meanwhile, during the afternoon and evening also on Monday 28 September, Corporate Aircraft Charter (South Australia) Cessna 550 Citation II bizjet VH-ZLE was noted also visiting Rockhampton Airport. It arrived from Brisbane and later departed to Longreach Airport before then returning to Rockhampton Airport and then Brisbane.
Photo taken by Steve Vit ©️