A missing woman from the St. Louis area was found strangled Thursday in a Cook County Forest Preserve near Des Plaines, authorities said.

Marquisha Williams, 29, went missing Dec. 20, according to a news release from St. Louis County police. On Friday, the Cook County medical examiner confirmed that a body discovered the day before in the Algonquin Woods near the 2100 block of East Algonquin Road was Williams.

An autopsy found that Williams had died of strangulation. St. Louis County police said Wednesday that prosecutors had charged her ex-boyfriend, Trenton Ivy, with first-degree murder.

Police said Ivy, a St. Louis resident, was in custody for unrelated charges in Racine, Wisconsin, and had confessed to killing Williams. He had been driving Williams’ vehicle, containing “apparent blood and biological materials” along with her personal items, when Racine law enforcement arrested him, authorities said. Williams was a mother of four, according to published reports.