Sandberg likely died of heart disease
Peoria County Coroner Johnna Ingersoll says Sandberg previously had heart surgery. The coroner says heat could have also played a role.
Sandberg's daughter last spoke to him on July 13. Colleagues and friends said they hadn't been able to reach him for days.
Sandberg served more than 20 years on the council. His term would have expired in 2015.