Williams was a drill instructor at the Cook County Boot Camp. He worked for the sheriff's department since 2006. Flags will be flow at half-staff and bunting will be hung Wednesday at boot camp in his honor, according to Cook County Sheriff Tom Dart.
"Although Derwin Williams was with the Sheriff's Office for a short time, his kindness and soft spoken manner had a great impact on everyone here," Sheriff Dart said. "He will be greatly missed and the thoughts and prayers of the entire Sheriff's Office go out to his family."
"Last night about 11 p.m. some soldiers came to my home and told me that my husband had been killed," Felicia Williams, Derwin Williams' widow, told ABC7.
On Tuesday night, Felicia Williams left Chicago to view her husband's casket when it arrives in Dover, Delaware on Wednesday.
"He would always tell me that his biggest fear of something like this was leaving hardship on me and the kids. We were his life. Everything he did was because of us," said Williams.
Williams is also being missed at Cook County Boot Camp.
Drill instructor Raymond Rodriguez, who trained with Williams, says he was the kind of guy who would literally give you the shirt off his back.
"I had some trouble, and he would stay late and waste his time and help me out. That's how we bonded and he'll be missed," said Rodriguez.
Derwin Williams also spent a year in Iraq in 2004. His wife says she could hear the difference in his voice when he would call from Afghanistan. He had a kind of fear she never heard when he was in Iraq.
Williams, 41, is survived by his wife, Felicia Williams, and five children. They live in Glenwood.
He is the second sheriff's office employee killed while serving overseas with the National Guard.