"I thought he was going to be dead. I thought that was it, straight away."
Several people rushed to help, including Mr Campbell and staff from the nearby Aurora Health Centre.
They found the man lying on the crossing but conscious.
A doctor ran a concussion test, which the man apparently passed, and he was able to recite his name and address.
However, he was suffering from an obvious head injury, Mr Campbell said.
"The impact he had was to the right hand side of the head, where there was a big hematoma."
Mr Campbell and the doctor helped the man up and assisted him to a waiting ambulance.
He was taken to Dunedin Hospital where his condition worsened and he died overnight.
Mr Campbell thanked everyone else who came to the man's assistance.
Police said the investigation by the serious crash unit was ongoing and a spokesman extended their thoughts to the man's family and friends.
This article was first published in the Otago Daily Times.