According the Chicago Sun-Times, newly released court documents show officers found a magazine article about staging crime scenes and one about making a death appear to be a suicide inside of Chris Vaughn's family home.
Court filings also show Vaughn spent time at a shooting range the night before his family was killed.
Police say the gun used at the range was the same weapon found between his dead wife's feet.
Vaughn --- who had also been shot twice --- claims his wife turned the gun on him and the children before killing herself.
The mother and children were found in the family's SUV near Channahon, on the way to Springfield.