A female ambulance officer was threatened with gun violence while a broken glass bottle was held to her neck during a recent callout to a remote part of Northland.
It was one of about 200 serious assaults against frontline ambulance officers that take place every year.
"She was scruffed, shoved and dragged back, but managed to escape prior to police and a back-up ambulance arriving. The assault has been reported to police," a spokeswoman for St John told the Herald.
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St John is throwing its support behind the Protection for First Responders and Prison Officers Bill, under New Zealand First MP Darroch Ball, which would see six months' jail for anyone intentionally hurting a first responder.
The member's bill is expected to complete its first reading in the House today and pass with cross-party support.
But Labour and the Greens may not support it beyond select committee, seeing as a mandatory minimum sentence would remove judicial discretion in the same way that the three strikes law does - which Labour and the Greens wanted to scrap, but couldn't without NZ First's votes.
The bill could still progress with only National's and NZ First's support.
St John director of people and capability Sue Steen said frontline ambulance officers were involved in or exposed to more than 2000 call-outs a year where they were either verbally or physically abused.
"Of these reported cases, 200 were serious and involved physical aggression and violence. Some were promptly resolved at the scene by police and some will be taken to court for prosecution.
"St John does not accept or tolerate any abuse or assault against any of our staff. We support the private member's bill and the introduction of tougher penalties."
Half of all crew abuse incidents over the past year involved alcohol or recreational drug abuse, while about 15 per cent could be attributed to mental health issues.
Most of them occurred in Auckland, Christchurch, Hamilton and the metropolitan areas, while over a third took place during weekends.
St John was also rolling out a work programme to end single-crewed responses, which was the case in the Northland assault.
The bill would create a new offence under the Crimes Act to protect first responders, defined as police, emergency health and fire service staff, and prison officers.
Injuring them with intent would see a mandatory prison term of at least six months - unless manifestly unjust. The maximum prison term would be 10 years.
The bill would also add first responders to the current charge of assault against a constable, prison officer, or traffic officer under the Summary Offences Act, which carries a maximum penalty of six months' jail or a $4000 fine.