(AP) — A recent spate of random, violent killings around Omaha have stood out, even in a city that about 80 percent of Nebraska’s homicides.

The cases include the May killings of a Creighton University professor and his wife in what police say was the work of a serial killer. In June, a 93-year-old woman was raped and beaten to death in her home. Earlier this month, the body of woman was found in a freshly dug cemetery grave. And on Wednesday, a mother of three was found shot to death in a suburban Omaha intersection.

University of Nebraska at Omaha criminology professor Ryan Spohn says the killings are unusual for their brutality and back-to-back occurrences and because the victims are “not who we think of as the typical homicide victim.”