Police said in a statement Thursday that 18-year-old Alexis Valdez is charged with one count of first-degree murder.
The Cook County medical examiner's office identified the victim as Sylvester Diaz-Hernandez. The office says Diaz-Hernandez lived at the apartment on the Northwest Side where his body was found early Wednesday.
Authorities didn't provide other details, including whether the decapitation occurred before or after the victim died. The medical examiner's office did say that Diaz-Hernandez died of "multiple blunt and sharp-force injuries."
Authorities also didn't explain the relationship between Valdez and the victim.
There was no telephone listing for Valdez in Chicago.
