CHICAGO (CBS) — When people found out Chicago Police Superintendent Eddie Johnson has a rare disease and needs a kidney, even strangers came forward.

Now CBS 2 has learned that Johnson’s 25-year-old son is one of the best matches, and as CBS 2’s Dorothy Tucker reports, they are both preparing for the operation.

“He said, ‘hey dad, you gave me life. I want to help prolong yours,'” Johnson said.

Daniel is the Superintendent’s middle child. He graduated from Knox college, where he played football. He now teaches at Oakdale Christian Academy.

“I’m proud of him because I know it’s not an easy decision, and it’s something he had to decide on his own, but I’m proud of him,” said Johnson.

Johnson was diagnosed with chronic kidney disease when he was 25-years-old. He first found out when he took the test to become a police officer. Since then, he’s controlled the disease with medication, diet and exercise. However, he was forced to go public with his condition when he almost fainted during a news conference.

As a result, Johnson has stepped up his exercise program. He recently shared his workout in a Facebook Live chat to encourage new police recruits to stay healthy.  He also revealed that he’s lost almost 25-pounds, which is part of the prep for his kidney transplant.

“When doctors prepare, they want you to lose as much weight as possible because that reduces your recovery time. So I started doing 40 minutes of cardio every day,” the Superintendent said.

And Johnson isn’t alone in the prep work. He said Daniel is also eating better and exercising, in hopes of giving his father the gift of life.

“I tell you, Dorothy, if I had gone to the store and picked a son, I couldn’t have done a better job than this kid. He is everything good about me. He’s the best that I have to offer,” Johnson said.

Since he found out he would need a new kidney, Johnson has been an active supporter of Gift of Hope Organ & Tissue Donor Network.

Watch & Listen LIVE