In the spring of 1971 a series of mass discoveries in Sutter County, California, revealed 25 shallow graves on orchards and ranches around Marysville and Yuba City. The victims were itinerant farmworkers and their bodies showed severe blunt and sharp trauma: chop and hack wounds to the head consistent with a heavy, sharp instrument and many also had stab wounds to the chest.

One of the victims was identified as Joseph Maczak. Although an initial date of death of August 22, 1971, appears in some accounts, that conflicts with the timeline of the graves being found between May 20 and June 4, 1971; it is therefore more likely Maczak died during the February–May 1971 period when the killings occurred. Personal items belonging to one man, including a candleholder, pieces of a broken mirror, a child’s sock and two Bank of America deposit slips bearing the name Juan Vallejo Corona, were recovered in Maczak’s grave.

Those items were used to link Corona to the killings; he was arrested and later convicted on 25 counts of first-degree murder.