After hearing a crash outside his house just after 10pm on Saturday, Rob Seddon raced outside to administer first aid to the driver and his passengers but he was allegedly punched and knocked out.
His son-in-law was also allegedly attacked and had his nose broken.
Seddon was airlifted to John Hunter Hospital in Newcastle where he underwent brain surgery.
“I could hear the sheer horrible noises from this guy that was being hurt, I had tears in my eyes, I knew it was bad,” neighbour Diane Gardner told 9News.
“It was absolutely horrible. You could hear his pain and he wanted help.”
The 17-year-old driver was arrested and charged with a number of traffic offences — including drink-driving on provisional plates.
NSW Police said they were still searching for all those involved.
“We’d also appeal for people to come forward. It’s too early to determine who was actually involved in the [alleged] assault,” Detective Chief Inspector Paul Nicholls said.