Mary Columbo, 41, of Elk Grove, Illinois, was one of three family members killed in their home on May 7, 1976. Mary and her husband Frank Columbo, 43, were shot. Their 13-year-old son Michael was bludgeoned with a bowling trophy and stabbed nearly 100 times with scissors.

Investigators later determined the murders were carried out by the Columbos’ daughter Patricia Columbo, 19 at the time, and her boyfriend Frank DeLuca, 39. Patricia had been living apart from the family for two years with DeLuca, who was married with five children. A tip from a friend prompted police to focus on Patricia and DeLuca. During the case, evidence emerged that DeLuca attempted to wash and burn bloodstained clothes and threatened witnesses; the couple were convicted and received very long prison terms, including additional sentences for conspiracy and solicitation to commit murder.

What details about the family’s life in Elk Grove or the events leading up to May 7, 1976, might help explain how this plan was conceived?