Frank Tereza stopped to help a stranger push a disabled car when someone hit him near Barrington and Bode Roads on Saturday.
Tereza's family said both of his legs were crushed. Doctors amputated one of his legs and were trying to save the other, but the damage was too great.
"He's so positive about everything, he's gonna make it through this and be great," said Quinn Groenwald, Tereza's cousin. "He's got so much family around him to support as well."
Police are still investigating the crash, but they say they have ruled out speed, alcohol or drugs as possible causes.
Tereza's family has set up a "Funds for Frank" GoFundMe account to help raise money for his medical bills.