Crump had moved to Australia in 2006 after a long career in emergency medicine in New Zealand.
He qualified as an ambulance officer in 1985 and Herald archives show Crump worked as a paramedic for St John and the rescue helicopter service in Auckland.
A spokeswoman for St John said Crump was qualified as an advanced paramedic and worked as a station officer and staff development officer during his time with the ambulance service.
"Mr Crump has nothing remarkable noted against his employment file and there were no allegations of inappropriate conduct during his time at St John," the spokeswoman said.
"St John considers his actions and offending in Australia to be completely unacceptable and entirely against St John's values and professional standards."
A former colleague remembered working with him at the Auckland Rescue Helicopter Trust and expressed surprise at the child sex convictions.
After his long service as a paramedic, Mr Crump started work as a combat medic in Iraq in 2004 as part of a private security team.
"My very first day we went through the streets of Mosul and we were stopped by a car bomb ... and I was told to get out and watch my perimeter. And I thought 'holy s***, what do I do? What am I supposed to look at?'. I had no idea," Crump told the Herald in a 2010 interview.
"I thought 'what the f*** am I doing?' I'm frightening a little old man and a little old lady. This is insane. I just smiled at them and said 'it's okay, I'm not going to hurt you'."