An ambulance was stolen as paramedics treated a patient inside their home.
The crew were dealing with an emergency on Green Lane in Deeside, Flintshire, on Saturday at 22:00 GMT when the vehicle was taken.
It was later found abandoned and damaged and had to be taken out of service.
The Welsh Ambulance Service NHS Trust (WAST) said it “could have led to very serious harm” if the patient had urgently needed to go to hospital.
Another crew was dispatched to assist colleagues when the theft was discovered.
“The theft of an emergency ambulance is an extremely irresponsible act placing patients and the public at risk,” said Bob Tooby, the ambulance service’s assistant director of operations.
North Wales Police, which is appealing for witnesses, said the damaged vehicle was located a short time later in Dee View Crescent.
“This has left the ambulance service with one less emergency resource and, ultimately, putting people’s lives in danger,” said a police statement.