Pfc. Victor Molinar Jr., who had graduated from Riverside-Brookfield High School last year, had just finished boot camp and was going through infantry training in San Diego.
Molinar was out with friends when he was hit.
Molinar's sister said he always wanted to serve his country and made his entire family proud.
He had planned to eventually return to the Chicago area to become a firefighter.
His body will be brought back to Chicago on Tuesday, his family said.