Mr Frizzell (66) was using a chainsaw and may have fatally injured himself while using the machinery. He was a well-known mechanic and married with grown-up children.
The only son Mark worked in the family garage along with his father.
It is not clear exactly what happened but the victim sustained injuries to his neck as a result of the incident.
He had gone to cut trees at 12.30pm in lands near his home at Augheygault and was found dead at 2.30pm by a daughter.
An investigation has been launched to discover how exactly the man died.
Emergency services rushed to the area but it is understood that Mr Frizzell died at the scene. Garda Supt Vincent O'Brien described the death as a "tragic accident".
Locals in the close-knit village have been left stunned by the man's tragic death.
The dead man's wife Sheila and his children were last night being comforted at their home.
One local said: "Norman was one of the hardest-working men you will ever meet. You would find the light on in his garage at all hours of the day and night because he was always working.
"This is such a tragedy. He never had a cross word for anyone and took so much pride in his work and helping people. It just doesn't seem fair that something like this has happened."
The accident comes less than two days after another tragedy claimed a man's life less than 15 miles away. Luke Peek (26) was killed on Christmas Day when his car left the road and ended up in a field close to Stranorlar.