"So the question is, why did they do it that way in the first place when we know that they're committed, we know they're genuine, they spend their entire working life helping patients?
"We got to the crash in good time, the system responded well, the intensive care paramedics arrived, they made an assessment, and there was an error in the assessment."
The man has been fighting for his life in the Royal Melbourne Hospital, but his condition has improved from critical to serious but stable.
Mr Sassella said Ambulance Victoria had offered to discuss the incident with the victim's family when they felt ready and was also supporting the paramedics involved.
"We are worrying for them and are looking after them," he said.
"Mistakes do happen. Unfortunately in our work when a mistake's made it can have horrible consequences, and in this case that's what's occurred."
Ambulance Victoria is next week due to release the findings from its investigation, which will involve medical experts and a review of the callout and events at the crash scene.
- AAP