South Carolina ? Investigators didn’t buy it when a woman said her two young sons drowned after her car plunged into a river. She ultimately confessed to killing the toddlers, they say — not by dumping them in the water but by suffocating them earlier with her own hands.

Broke, jobless and berated by her mother for her failings, Shaquan Duley killed the boys, ages 2 years and 18 months, then strapped their bodies into their car seats before rolling the vehicle into the North Edisto River in a desperate cover-up attempt, authorities said Tuesday.

“She truly felt, ‘If I don’t have these toddlers, I can be free,'” Orangeburg County Sheriff Larry Williams said at a news conference. “I think she was fed up with her mother telling her she couldn’t take care of the children, or she wasn’t taking care of the children and just wanted to be free.”

Coroner Samuetta Marshall said Tuesday the older boy had bruises that suggested he had been in a struggle.