The fire broke around 9:15 p.m. Monday in a three-story apartment building in the 1800-block of 51st Avenue in Cicero, officials said.
First responders found Jesus Daniel Nunez Campana dead inside after the fire was extinguished, police said. He died of a gunshot wound to the head, the Cook County Medical Examiner's Office said.
His roommate, Naman Alfredo Vazquez, was arrested in New Mexico on a charge of possession of a stolen vehicle believed to belong to the homicide victim, officials said.
Cicero police said Vazquez was facing an aggravated arson charge and is now awaiting extradition back to Illinois. It was not yet known if additional charges will be filed.
No further information from local authorities was immediately available.