Did Robert Butler, Jr., the school shooter in Omaha, NE, have any siblings?

The only information that I could find about his family is that his parents are divorced, and the mother remarried. She lives in Lincoln, NE, where Robert was attending school; she sent him to live with his father, an Omaha police detective; at this time he switched to Millard South High School. He shot and killed the school's istant principal on Tuesday, January 5, 2011. He also critically wounded the school's principal.