Story highlights Prosecutors say grandmother killed infant with sledgehammer, knife

Alfreda Giedrojc has been charged with first-degree murder and is held without bail

Investigators say she expressed remorse for the child's death

Left to babysit her 6-month-old granddaughter, a suburban Chicago woman instead turned on the infant, bludgeoning her and cutting her throat, prosecutors said Monday.

Alfreda Giedrojc is being held without bail after a court appearance Monday afternoon, said Tandra Simonton, a spokeswoman for the Cook County State's Attorney's office. She was charged with first-degree murder in the death of her granddaughter, Simonton said.

The girl's father brought her to Giedrojc's home in the southwestern suburb of Oak Lawn on Sunday while he helped with repairs on a nearby home, Simonton told CNN.

"Her father and grandfather had stepped out of the grandparents' house for a short time when this horrific event took place," Oak Lawn police said in a written statement on the death.

While her husband was away, Giedrojc laid the child on the floor, pulled a sledgehammer from a nearby closet and swung it down on her head and body several times. She then picked the baby up and used a carving knife to slit her throat when she was still alive, Simonton said.

Oak Lawn Det. Mike Kaufmann said the 61-year-old Giedrojc expressed remorse for the child's death when questioned, and investigators have found no record of previous arrests or mental illness.

Attempts to reach the public defender assigned to represent Giedrojc were unsuccessful Monday evening.