Boy, 7, in tragic mercy dash

A 7-year-old boy has been praised for a mercy dash after his father was electrocuted by a fallen power line and his mother was left severely injured with serious burns.

Ethan Walker ran to raise the alarm after father Brendon, 39, was killed when he rode his quad bike over a power line carrying more than 1000 volts on the North Canterbury farm where he was working.

Mr Walker was discovered by wife Sarah and Ethan when they went out to check the letterbox for mail.

Mrs Walker tried to help him but suffered severe burns to her hands and feet.

Constable Jon Eagle was full of praise for Ethan. "This young man has been confronted by everyone's worst nightmare but has had the presence of mind to run back to the house and call for help."

Friends and neighbours of the Walkers have been devastated by the tragedy, describing it as a "raw time" for the district.

On Saturday morning, Mr Walker headed out to check his cattle and when he saw three lying in the paddock, he drove his quad bike over for a closer look, said Mr Eagle.

But he drove over the same power line that had killed the cows and was electrocuted.

Mrs Walker was hurt when she tried to help her dead husband.

"The 7-year-old boy reports touching his father," said Mr Eagle, "but luckily there was no current or anything there so he didn't get a shock himself. He described his father as clicking, so obviously he could hear power there somewhere."

Ethan ran home - about 250m - and told his sister, Allanah, 9, before they phoned their grandmother in Queenstown, who called 111.

"It's an isolated rural farm," said Mr Eagle, "and if it wasn't for his actions, we wouldn't have been there as soon as we did."

Mrs Walker was airlifted to Christchurch Hospital, where she remained last night in a stable condition. Mr Eagle said she was answering questions, but was still quite "tired and confused".

Relatives from around the country had gathered to be with the children, who had been to see their mother in hospital.

Brendon's brother Scott Walker said Ethan and Allanah were doing well and were with family - including six cousins aged 4 to 12.

He said his brother was a good man who was loved and would be missed.

Scott Walker said he and his family wanted to thank neighbours and the emergency services who helped Brendon and Sarah.

He said his sister-in-law was "up and about" and was waiting to hear whether she would need plastic surgery.

The cause of the tragedy has been established. "There has been a small fire at the top of the power pole, which has burnt through the power pole itself and it's released the bracket that holds the insulators that are attached to the wire," Mr Eagle said.