James C. Dunham was born around 1864 in Santa Clara County, California. His mother, known for her volatile temper, passed away in 1893. Dunham's early life was marked by instability; he held various jobs, including nurseryman, bicycle agent, and orchardist. In 1895, he married Hattie Wells, the daughter of Ada Wells McGlincy and stepdaughter of Colonel Richard McGlincy. The couple lived on the McGlincy family orchard in Campbell, California.

Dunham's relationship with his in-laws was strained. He was perceived as unreliable and had a history of financial irresponsibility. At the time of the murders, Dunham was studying law at Santa Clara College, having enrolled in February 1896.

On the night of May 26, 1896, James C. Dunham committed one of the most heinous crimes in California's history. Armed with two revolvers and an axe, he murdered six members of his household:

Hattie Wells Dunham (wife)

Ada Wells McGlincy (mother-in-law)

Colonel Richard McGlincy (stepfather-in-law)
James Wells (brother-in-law)
Minnie Schlessler (household servant)
Robert Brisco (household servant)

The attack began late in the evening when Dunham strangled his wife and killed Schlessler with an axe. He then murdered his mother-in-law in a similar fashion. Upon the return of Colonel McGlincy and James Wells from a meeting, Dunham ambushed them, resulting in their deaths. Brisco was also killed during the rampage.

A farmhand, George Schaible, managed to hide in the barn and survived the massacre. Dunham's three-week-old son, Percy Osborne Dunham, was also spared.

Following the murders, Dunham fled the scene, initiating an extensive manhunt. Despite numerous sightings and leads, he was never apprehended. Theories about his fate range from suicide in the nearby mountains to escape to Mexico or Cuba.