/ CBS/AP

Authorities made two gruesome discoveries Tuesday after a Missouri woman walked into a police station and told officers that she fatally shot one of her children and drowned the other, officials said. Jefferson County Sheriff Dave Marshak said at a news conference that authorities believe both children were killed Tuesday morning.

Ashley Parmeley, 36, of Pevely, is charged with second-degree murder, authorities said Tuesday night. She is being held at the Jefferson County Jail without bond.

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Ashley Parmeley Jefferson County Sheriff

A 9-year-old girl was found dead inside the mother's car, which was parked outside the Festus police station, where the mother turned herself in.

Parmeley's clothing was wet when she arrived at the police station, CBS affiliate KMOV-TV reported, and Marshak said the other child had been drowned elsewhere. A 2-year-old boy was found dead in a fountain outside a resort near Festus, a suburb of St. Louis.

Marshak said officers searched for a third child who has been found safe.

Parmeley was arrested and the deaths are being investigated as homicides. Authorities have not disclosed a possible motive.

Parmeley is currently only charged in connection with her son's death but the Jefferson County Sheriff's Office says it intends to ask prosecutors in St. Francois County to charge her in connection with her daughter's death, KMOV-TV reported.

The Festus School District confirmed that the girl had just completed 3rd grade at Festus Elementary School, the station reported.

"We extend our deepest sympathies to the families of the victims and all the first responders who were touched by this tragedy," the sheriff's department said in a statement.