This is some data: Vacant DATE_SUCCESSOR_SEATED Not filled this term; Illinois's 4th VACATOR George M. O'Brien (R); George M. O'Brien (R) REASON_FOR_CHANGE Died July 17, 1986; Illinois's 4th SUCCESSOR Vacant.

Generate a detailed description of this data
After O'Brien's death on July 17, 1986, the seat remained vacant for the rest of the term.