A DeKalb woman was charged with murder after she was accused of slamming her boyfriend's two-year-old son to the ground, causing severe brain injuries, authorities said.

Alexandra Hoyle, 21, was initially arrested Nov. 11 on a charge of aggravated battery to a child as the boy, Khalil Body, was being treated at Ann & Robert H. Lurie Children's Hospital of Chicago, DeKalb police said in a news release

Hoyle's charges were upgraded after Khalil died of his injuries Wednesday, police said. Khalil's death was ruled a homicide due to blunt force head trauma and child abuse, according to the Cook County medical examiner's office.

"The tragic loss of a two year old child at the hands of this offender is unthinkable. On behalf of the DeKalb Police Department we offer our sincere condolences, and our thoughts and prayers are with the victim and those that survive him," DeKalb Police Chief Gene Lowery said in a statement.

Police opened an investigation Nov. 10 after Northwestern Medicine Kishwaukee Hospital notified them that Khalil suffered a severe brain injury under suspicious circumstances, police said.

Working with DeKalb County State's Attorney's Office, police determined that Hoyle, who was dating Khalil's biological father, caused the injuries by slamming the child's head onto the hardwood floor at his home in the 800 block of Ridge Drive, police said.

After her initial Nov. 11 arrest, Hoyle posted a $100,000 bond on the child battery charge and was released from the DeKalb County Jail on Tuesday, police said.

An additional warrant was issued for Hoyle after Khalil's death and she was booked back into the jail on two counts of first degree murder, police said. Her bond was set at $750,000, according to online DeKalb County court records. She remains in the jail, police said.