This unnamed rugaru was the father of Jack Montgomery.
This man lived an ordinary life as a dentist until he began transforming into a rugaru in 1978 and killed eight people. The hunter Travis promptly killed him. The man's wife, who was pregnant at the time, gave their son up for adoption. Convinced the child had the rugaru gene within him, Travis kept an eye on the child, now known as Jack Montgomery, until the child showed signs of transforming.
After thirty years, Jack began his transformation, leading Travis to try and kill Jack along with Jack's pregnant wife.
Jack himself, being at the very last stage of his transformation, attacked and killed Travis, avenging his father. However, Jack himself was killed by Sam Winchester, for he had become too dangerous to let alone. Meanwhile, Jack's wife fled the house, leaving her whereabouts and her child's unknown. This also led to his Rugaru bloodline continuing on in his grandchild.