The reports of the incident I found were as vague as this article.
Charles Winter was know to be violent and brutal. He was very strong and tough, and had beaten up many people.
Charles Winter had repeatedly threatened Gilbert Grooms and his family.
Grooms wife and daughters were close by.
Grooms has had numerous injuries and surgeries, and could easily have been maimed or killed by Winter.
At one point, Charles Winter was charging Grooms.
After being shot, and being held for police, Charles Winter again threatened Grooms, saying: "Maybe you won't be so lucky next time."
Charles Winter also lives on the reservation. When Grooms complained to the tribal police about Winter, they did nothing.
The only reason Winter is alive, after the incident, is Grooms was careful to not kill him.