No ambulance was sent to the aid of a shot and dying Otaki Beach woman this month because staff were busy on other calls.

The 23-year-old mother was allegedly shot by her partner on May 8. Firefighters and police gave her first aid but firefighters became so concerned with the St John response they called off-duty paramedics to the scene themselves, the Dominion Post reported.

The paramedics arrived 25 minutes after emergency services were called and borrowed the firefighters' medical equipment to treat the woman. She then had to wait 41 minutes for a helicopter and a paramedic to arrive from Palmerston North.

She died the next morning in Wellington Hospital and her partner has been charged with murder. Both have name suppression.

It is understood the Fire Service has written to St John asking it to explain its delay in treating the woman, the paper reported.

St John said yesterday that it had not received any formal letter but that its on-duty Otaki staff had been on their way to Palmerston North with a patient when the shooting occurred.

Two ambulances in Levin were responding to another call, after the cardiac arrest of a terminally ill cancer patient, who was the subject of a non-resuscitation order.

St John said sending the rescue helicopter, with an advanced St John paramedic on board, was the best option. "Every effort to send appropriate resources to this incident was made."

Palmerston North rural police area commander Brett Calkin said officers attending the shooting scene had not raised any concerns about the St John performance.