Billboard.com said the performer, who released the song "3hunna K" in April, died Tuesday night after months of feuding with fellow rapper Chief Keef and his crew.
"Its Sad Cuz Dat Nigga Jojo Wanted To Be Jus Like Us #LMAO," Billboard.com said Keef tweeted shortly after his rival died.
Keef later denied he wrote the message, claiming his Twitter account had been hacked, Billboard.com said.
The Chicago Tribune reported police are investigating whether the shooting was part of a gang conflict.
A witness told police Coleman was riding a bicycle when he was shot by a gunman in car, the Tribune said.
No arrests have been made in connection with the shooting.