Richard Castellana, 55, lived in suburban Tinley Park.
Castellana served Cook County for 35 years and retired in 2019, according to the Cook County Sheriff's Department.
On Friday, Castellana was outside of the First Midwest Bank located at 1975 W. Ridge Road in Gary when two male suspects, armed with a handgun and a rifle, apparently ambushed him, the Lake County Sheriff's Department said.
CREDIT: Lake County Sheriff's Department
Police believe the suspects then entered the bank and demanded money.
The sheriff’s office used K-9 units to track down the gunmen, the sheriff’s office said. Hours later, officers took one of the suspects into custody.
A manhunt is still underway for the second suspect.
The Cook County Sheriff's Department released the following statement:
"We are saddened to hear about the tragic passing of our former Deputy Sheriff, Richard Castellana. Deputy Castellana served Cook County for 35 years until his retirement in 2019. He will be greatly missed by his colleagues and friends. We send our deepest condolences to his family and loved ones."
The FBI has taken over this case as the investigation continues.
The Sun-Times Media Wire contributed to this report.