Boyd shot 56-year-old Sharon Goffard in the abdomen from about 6 feet away.
According to the district attorney, "It appears to be, from all evidence I've seen, an isolated incident between these two regarding what looks like a dispute over positions at the Walmart."
Goffard's boyfriend told reporters that Boyd had recently confronted Goffard about her new position in the liquor department, which Boyd deemed to be easier.
In addition to the handgun used to shoot Goffard, police found a Taurus Rossi .38 special revolver in Boyd's bag.
Boyd has been charged with first-degree intentional homicide. Goffard was admitted to the hospital in critical condition.