(CBS) — The lead private investigator who spent more than a decade looking into the disappearance of the two Bradley sisters has died, and the Bradley family says they are feeling the loss.

Shelia Bradley Smith is the great aunt of Diamond and Tionda Bradley and family spokeswoman.

She says she has learned investigator Jim Miller passed away. He went to work on the case in 2005 — four years after the girls disappeared from their South Side home.

Miller and Investigative Services Agency stepped up to help, pro bono, says a grateful Smith.

“Jim Miller and his team actually went over to Morocco when there were rumors the girls were overseas. He went there. He went to California. There was just no boundary he wasn’t willing to go to find Diamond and Tionda.”

Smith says she extends sympathy to the family, and she says she feels Miller’s death is a setback for the case.

A business associate says Jim Miller died of cancer. He was 58.