The incident happened July 11 near the 1400 block of E. 13th Place in Ford Heights.
Ronald Wade, 18, has been charged with aggravated battery, but additional charges are now likely.
Bond was set Friday at $2 million for the south suburban teen.
Witnesses say the struggle over the bike escalated, with Wade beating and choking the 48-year-old man before throwing him to the ground.
The unidentified man was in a coma at Stroger Hospital and died Saturday from his head injuries.