A Chicago grandmother who was supposed to be looking after her granddaughter instead brutally murdered the infant, police say.

Alfreda Giedrojc, 61, was left to babysit the 6-month-old child while her grandfather went across the street to visit another relative Sunday morning, CBS Chicago reported.

Alone with the child, Giedrojc allegedly laid her on the floor and grabbed a sledgehammer that she had placed in a closet the night before. Prosecutors say Giedrojc then swung the hammer down on the baby's head and body several times. The baby was still moving and crying, so Giedrojc took a carving knife, picked the baby up, and slit her throat, Cook County State Attorney Spokeswoman Tandra Simonton told CNN.

The child was rushed to Advocate Christ Medical Center and pronounced dead shortly before 2 p.m. Giedrojc was ordered held without bond Monday on a charge of first-degree murder, the Chicago Tribune reported.

"I have never seen anything like it," Oak Lawn Police Chief Mike Murray said. Murray said officers who responded to the call have been offered counseling.

Oak Lawn Det. Mike Kaufmann said the Giedrojc (Giedrocz in some publications) expressed remorse for the child's death, and investigators have found no record of previous arrests or mental illness.

The Chicago Tribune reports the grandmother's last name as "Giedrocz." Other publications, including CNN and CBS, have spelt the last name "Giedrojc."

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