Johnathan Fair, 19, of the 1600 block of Sunset Avenue in Waukegan.

A 4-year-old Waukegan girl who was hospitalized last week has died as a result of child abuse injuries. Her mother’s 19-year-old boyfriend has been charged in connection with her death.

Johnathan Fair, 19, of the 1600 block of Sunset Avenue in Waukegan, was arrested on Friday and initially charged with aggravated battery to a child. Additional charges are expected following the young girl’s death.

Waukegan Police Chief Wayne Walles said that officers were called to Vista East Medical Center for a 4-year-old girl with a head injury. Police were initially told that the child, identified as Skylar Mendez, suffered the injury after falling in the couple’s apartment.

Skylar was brought to the hospital by her mother and Fair, who both live together in the 1600 block of Sunset Avenue in Waukegan. Police investigators determined that the girl did not sustain injuries from a fall but was actually injured as a result of physical abuse by Fair, Walles said.

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Walles added that Fair and the 4-year-old girl were alone in their apartment at the time of the incident. The girl’s mother was not home.

Skylar was in critical condition at Lurie Children’s Hospital of Chicago where she died early Sunday morning. An autopsy conducted by the Cook County Medical Examiner’s Office showed that she died from multiple injuries caused by child abuse.

Her death was ruled a homicide. Fair remains held in the Lake County Jail on a $5 million bond. He is scheduled to appear in court again on January 9.