The escape took place on Thursday shortly after midday in Kleve, on the Dutch border.
A 27-year-old who was being held in a psychiatric ward was being taken to the doctor by two psychiatric nurses.
As the man stood handcuffed before the doctor's practise, a young woman walked up to the carers, drew a gun and demanded that they release him.
Police suspect that the woman is a 22-year-old who has previous convictions as an accomplice to the man's crimes.
The two then stole a nearby Volkswagen Golf and drove off. The Golf was found later, crashed on the road to Goch. The two appear to have fled further on foot.
The man has a long police record and may be armed.
Although the police have used helicopters and sniffer dogs in a wide-ranging search effort, they have still found no trace of the pair.