(CNN) — The grandmother and stepmother of a 9-year-old Alabama girl who died Monday after allegedly being ordered to run around her family’s house — for hours — as punishment for lying about taking a candy bar have been charged with murder, police said Wednesday.

“Joyce Hardin Garrard, 46, and Jessica Mae Hardin, 27, were both arrested and charged with murder in connection to the death of Savannah Hardin,” Capt. Jeremy Walker said in a news release issued by the Etowah County Sheriff’s Office. Garrard is the child’s grandmother and Jessica Hardin is her stepmother.

At about 6:45 p.m., the stepmother called 911 and said that Savannah, who had run for about three hours, had suffered a seizure and was unresponsive, the release said.

“A very unnecessary act,” said Etowah County District Attorney Jimmie Harp in a telephone interview about the incident, which occurred Friday. “(The) taking of a candy bar turned into (an) all-day marathon … until the point of time she just collapsed.”

Savannah Hardin died Monday at Children’s Hospital in Birmingham; a state pathologist in Huntsville ruled her death a homicide. “Preliminary reports show Savannah was extremely dehydrated and had a very low sodium level,” the release says.

“It’s sad when a family is grieving over the death of a daughter and granddaughter and so soon to find out that the death could have been prevented,” said Sheriff Todd Entrekin, whose office became involved after witnesses called investigators to express concerns. “We have always said that we will protect the rights of those who cannot defend themselves,” he continued.

Savannah was a third-grade student at Carlisle Elementary School.

Garrard and Hardin were being held in the Etowah County Detention Center in lieu of a $500,000 cash bond.