MURPHY, N.C. (AP) — A North Carolina woman has been charged with killing her twin 4-year-old sons, whose bodies were discovered by their father when he arrived to pick them up, authorities said.

The father called 911 after he arrived at the home of his wife, Genevieve Ellen Springer, on Saturday morning in Murphy, North Carolina, according to the Cherokee County Sheriff’s Department. The couple were separated, so the father had come to the home for a custody exchange.

Authorities are trying to determine when the children died. The father, who was not named by authorities, said he last saw them alive Feb. 26. A statement by the Cherokee County Sheriff’s Department said an autopsy will be performed on the victims that should help determine when they died.

Springer has been charged with two counts of first-degree murder and was being held without bond in the Cherokee County Detention Center. The sheriff’s department said she was briefly hospitalized after her arrest Saturday.

In the statement about the slayings, Cherokee County Sheriff Dustin Smith asked for prayers for the victims’ family, friends and the first responders involved in the incident.