"I was standing a good distance away from the water but Ian came shooting past me and he hit some slippery rocks. I saw him do a big back flip into the air and fall into the water. I ran for him and grabbed on to him but I couldn't hold on any more.
"The force of the water just pulled him from me.
"He shot around and grabbed on to another set of rocks at the top of the waterfall. I called for Paula, another workmate, to come help. We both had a grip of him but we couldn't hold on," he said.
Randall fell 12m to the bottom of the waterfall.
His colleagues ran to the base of the falls but Randall had disappeared.
"We stayed there for about six hours to help the police and search and rescue teams. It was awful," said Smith.
Randall came from England but had lived in New Zealand for four years with his wife Susie and their two young children, Leonie and Oscar.
His brother Barry told the Herald on Sunday from the United Kingdom that Ian had many friends.
Randall's funeral will be held on Friday at 10.30am in the Rangiora Chapel.