When ambulance officers couldn't save people's lives family sometimes became aggressive, he said.
"We understand that in times of emotional crisis outbursts from family can turn into anger and aggression. It's a natural human response and people sometimes apologise afterwards.
"But there are also people who are just abusive by nature."
St John paramedics attend about 130 call-outs a week and are abused multiple times a week.
Mr Riedinger said it was mostly verbal but sometimes escalated to physical abuse which St John had a zero tolerance policy on.
"We always involve police if an officer feels threatened or in danger."
If a callout is dangerous, ambulance officers alert police who attend the job with them.
Senior Sergeant Ewan Dunmuir said in those extreme situations, police entered first and did an initial risk assessment to check it was safe.
On average police are called out to support ambulance officers once a week.
Mr Riedinger said even with police support sometimes dangerous situations prevent ambulance officers from doing their jobs and they had left scenes because the risk was high.
All St John officers participate in the Stay Safe programme which teaches them to recognise dangerous situations and minimise risk.
Mr Riedinger said he tried to find out where the abuse stemmed from and then worked out how to deal with it.
He said unfortunately abuse was part of the job but the majority of New Zealanders had a high level of respect for the ambulance service.
