Prosecutor James Glasgow said Christopher Vaughn, 32, was charged with eight counts of first-degree murder, CBS News reported.
The bodies of Kimberly Vaughn, 34, and the couple's children -- Abigayle, 12, Cassandra, 11 and Blake, 8 -- were found June 14 in a sport utility vehicle parked on a service road near Interstate 55 in Channahon, about 40 miles southwest of Chicago.
Police found the bodies after getting an emergency call from a passer-by flagged down by Christopher Vaughn. A pistol was found at the scene.
Christopher Vaughn had been shot in the thigh and was not initially labeled a suspect, CBS said. The computer forensic adviser was treated and released the same day as the shootings.
Investigators at one point have viewed the May 8 episode of the TV crime drama "Law & Order," in which a mother supposedly shot her children to death, wounded her husband and then took her own life.
The NBC show ends with police arresting the husband on charges of killing his wife and children, The Chicago Sun-Times reported.