Trent Mettam had been expecting a day of stray dogs and illegal campers when a woman ran up to his car with her unconscious son in her arms.

The Shire of Wyndham East Kimberley ranger was patrolling the Kununurra suburb of Lakeside when he noticed a car reversing out of a driveway.

The vehicle sped up and hit a house. The next minute, a woman ran to Mr Mettam's car window with an unconscious three-year-old boy in her arms.

"He had a bone sticking through his leg and his arm was broken," Mr Mettam said.

The pair hopped into Mr Mettam's work car and he headed straight for hospital but, on the way, the boy stopped breathing.

Quick thinking on the roadside

Mr Mettam said he had to think quickly and proceeded to give the boy CPR.

"I hadn't witnessed anything like this before, let alone be the first responder," he said.

"My hand was bigger than the little boy's chest, so it was quite scary. I didn't want to do anything irrational."

He then wrapped his shirt around the boy's leg to stop the bleeding before continuing to hospital.

The boy was later flown to Darwin for emergency surgery.

The three-year-old boy was injured in this crash in January 2018. ( Supplied: WA Police )

A full recovery

Mr Mettam said he did not keep in contact with the family after the accident, but he was phoned by Major Crash Investigation for a report.

"They did mention that the little boy made a full recovery and, if it wasn't for myself being there at the time, he probably would have died," he said.

But witnessing the accident, which happened in January last year, left its mark.

"It went through my head for quite a while, what had actually happened," he said.

"I did, at one stage, think I should speak to somebody just to get it off my chest. Not that it was bothering me, but I wanted to speak about the accident and what it was like.

"I didn't think that much more of it after that — once I got feedback he was okay it sort of cleared my mind."

Community hero award

Mr Mettam has been presented with a St John Ambulance Community Hero award by WA Governor Kim Beazley in recognition of his actions.

The award is given to people who have displayed exceptional judgement, bravery and skill to deliver care to someone during a medical emergency.

An officer from the Major Crash Unit made the nomination and noted that Mr Mettam spent his day off volunteering at a sausage sizzle for the Australia Day public holiday just two days after the crash.

Mr Mettam said it was nice to be recognised but urged everyone to consider learning basic first aid, regardless of whether it was a job requirement.

"I think basic first aid training is essential for anybody and everyone should get in there and have a go," he said.

"If I didn't have it at the time I don't know what I would have done or if we would have even made it to the hospital."