Orland Park police said officers responded at about 12:03 a.m. on March 20 to a report of shots fired in the area of 170th block of Redbud Lane in the Orland Ridge Towns and Villas.
Mechellea Williams, 28, was found dead inside a vehicle at the scene, police said.
Two men and a woman are now facing charges in connection to the murder, authorities announced Wednesday.
The male suspects, 29-year-old Kiraun Williams and 28-year-old Tyshann Boyd, are both from Chicago, police said. The female suspect, 20-year-old Alexis Hernandez, is from Crete, Illinois.
Williams was arrested by the FBI on August 15 in Las Vegas, Nevada, and he has been charged with First Degree Murder, Orland Park police said.
Boyd was arrested August 20 and charged with Possession of a Stolen Motor Vehicle and Unlawful Use of a Weapon by a Felon, police said. Hernandez was arrested August 12 and charged with Obstructing Justice.
Williams was flown to Cook County on Tuesday and appeared before a judge Wednesday for the First Degree Murder charge, police said. He was ordered to be held in custody until his trial.
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The president of the National Association of Letter Carriers Branch 11 of Chicago, Elise Foster, told ABC7 in March that the mother of three had been working as a postal worker in downtown Chicago for 8 months prior to the shooting.
"No one wants to get that news... go out to the family," Foster said. "She's just a great person. A young lady coming to work to, you know, make a living for her family, and she was just an excellent worker."
Family members of Williams were left reeling from her death and baffled by what happened.
"It's real tough, because we're all out here just trying to seek some answers, and hopefully someone will speak up and come forward," the victim's cousin, Breanna Williams, told ABC7 in March. "It's devastating, honestly. All of that is a mystery that we're trying to solve."
The South Suburban Major Crimes Task Force has been working with police to investigate the shooting.