The Cook County medical examiner's office identified the man as Davy Easterling, 31, and said his body was found Friday in an apartment on the city's South Side, the Chicago Tribune reported Sunday.
Authorities said Easterling was found in a rear bedroom with gunshot wounds to the throat and chest, the Chicago Sun-Times reported.
On Friday, Twista, whose real name is Carl Terrell Mitchell, posted messages on Twitter and Instagram, saying that Easterling had been missing for three days.
Mitchell said Easterling, who acted as a bodyguard, was a "close friend of mine."
On Saturday, Mitchell tweeted: "#RIP Davy Easterling aka 6'9 I have lost too many good friends to these streets."
Police were conducting a homicide investigation, the Tribune said.
Investigators determined that the fire was intentionally started and it was being investigated by a bomb and arson squad, Chicago Fire Department spokesman Larry Langford said.