Police say Doran W. Bloom, 27, of Marengo, entered the home of John and Audrey Feldkamp, ages 83 and 81 respectively. Their son, Scott A. Feldkamp, 54, who lives in Florida, was visiting his parents when the attack happened.
Police say Bloom, a neighbor of the Feldkamps, stabbed all three of the residents. The intruder was then shot and killed by the couple's son.
Scott Feldkamp was transported to Sherman Hospital in Elgin for treatment. He suffered a punctured lung but is recovering. Audrey Feldkamp was flown to St. Anthony's Hospital where she was later pronounced dead.
Police say Bloom has a history of mental health issues.
"We can find no motive for this. We can find no connection between the offender and the victims in this matter," said Sheriff Keith Nygren, Mchenry County.
Nygren says that Bloom had been on medication for mental health issues since he was a teenager and would experience episodes of rage. Investigators say they don't know how Bloom gained entry to the Feldkamps' house but he first stabbed John Feldkamp with a folding knife.
Scott Feldkamp fired several shots that killed Bloom right after Bloom stabbed Audrey more than a dozen times.
"During the attack, he was able to break free from the offender and go to an upstairs bedroom and retrieve a firearm that was kept in the house," said Nygren.
Investigators say Bloom's parents are cooperating and that no charges will be filed.
"I'm sure they're devastated by what has happened not only to their neighbors but to their son. I mean, this is a horrible tragedy for everyone," said Spencer Prahl, a neighbor of the Feldkamps. "I have been around 72 years and nothing has ever happened like this before, never hit so close to home...it is hard to digest it all. It really is."
Sheriff Nygren stressed that the stabbings seem to be a random incident and that neighbors should not be fearful.
John Feldkamp designed and built the home which the couple lived in for several years. Neighbors say the Feldkamps developed the subdivision that they all lived in and would throw a big Fourth of July party every year. They call their deaths a terrible loss.