A 48-year-old woman was convicted and sentenced to life in prison without parole Wednesday for killing a 16-month-old boy in her care.

A jury found Mary Spence guilty of malice murder, felony murder, aggravated assault, and cruelty in the first and second degree in the death of Samuel Miller, the Fulton County District Attorney’s Office announced Thursday.

The displaced skull fracture the toddler suffered was caused by a force consistent with a fall from a two-story window onto a concrete sidewalk, the medical examiner testified.

Spence was babysitting Samuel and two of her grandchildren on April 3, 2011, at a Carver Homes apartment in Atlanta when the incident occurred.

Prosecutors said a frustrated Spence violently shook the child and threw him against a hard surface repeatedly because of his constant crying. When the injured boy became unresponsive, Spence went to a neighbor, who told her to call 911. Samuel was pronounced dead within 15 minutes of being transported to a hospital.

Spence told authorities that Samuel fell and hit his head, but her 5-year-old grandson said he saw her shake Samuel and throw him against the wall several times, the DA’s office said.

At the time of her arrest, Spence was also wanted in Florida for violating probation related to a 2005 child cruelty case, officials said. In that case, she had pleaded guilty to charges involving burns to a 2-year-old’s feet.