A Pickens County woman shot and killed her two sons, her ex-husband and her stepmother, then tried to make it look like her son was the killer to collect life insurance policies on all the victims, authorities said Tuesday.

Susan Hendricks was arrested Monday night and charged with four counts of murder, Pickens County deputies said.

Hendricks, 48, was in one of two homes where the shootings happened. She told deputies at the time her youngest son had been using drugs and was suicidal. Officers found a gun by his body, and Hendricks said he left her a note on the kitchen table.

But investigators said Tuesday it was all staged.

"Her statements were inconsistent with the scientific and forensic evidence," Solicitor Walt Wilkins said in a news conference in Pickens.

Prosecutors would not say how much insurance Hendricks had on the victims, but it was a significant amount.

It wasn't immediately clear if Hendricks had an attorney. The only time she talked to reporters after the killings was a statement asking for privacy.

All four victims were shot. Matthew Hendricks, 23, was found dead in his bed with a gun beside him. The body of Susan Hendricks' stepmother, 64-year-old Linda Ann Burns, was found inside another bedroom in Hendricks' home. Next door, authorities found the bodies of her 52-year-old ex-husband Mark Hendricks and her other son, 20-year-old Marshall Wayne Hendricks. Both had been shot in the chest.

The homes are about five miles outside Liberty, in an area of mixed farms and suburban residences in the state's west.

This isn't the first deadly shooting at Susan Hendricks' home. The coroner's office said in April 2006 that 36-year-old Doyle "Brian" Teague was shot to death after entering the house uninvited and threatening someone inside.

Investigators ruled at the time she acted in self-defense.

Pickens County Sheriff David Stone defended his decision not to immediately arrest Susan Hendricks. She was taken into custody nine days after the killings.

"In a case of this magnitude, but where there appears to be no significant risk to the public and the suspect can be readily monitored, prudence dictates that sufficient forensic tests be done prior to an arrest being made," Stone said.