Senior Sergeant Dylan Earle said Mr Reid had moved on to cut another pine when the first tree became free and fell on him.
Mr Reid was working in partnership with another person who was about 100 metres away in a loader at the time.
Mr Earle said the deceased was an experienced worker who had been with the Wanganui crew for about four months.
Investigators from the Ministry of Business, Innovation and Employment attended the scene and would conduct their own investigation.
The accident has been referred to the coroner.
Council of Trade Unions president Helen Kelly said the death showed the industry needed a "rigorous review into its employment practices".
Ms Kelly said the industry was controlled by a few very big forest owners who largely contracted out cutting work to small employers who are forced to compete on price to win work.
She said this practice led to long working hours, low pay, higher risks and extreme working conditions.
She also called on the Government to immediately establish a group to communicate with forestry workers and make recommendations to improve safety measures.
Glen Mackie, senior policy analyst of the Forestry Owners Association, said the death was tragic but he believed health and safety practices were improving in the industry.
"We're not happy when any serious incident occurs.
"We have an active health and safety programme. We are a high risk hazardous industry which has to be recognised but we are improving year-on-year," Mr Mackie said.
"We have a goal of zero serious harm incidents and we are working towards that goal."
The forest owner and employer involved in yesterday's incident could not be identified.
