His 56 year old father, Hy Sock was charged Friday with first degree murder in the stabbing death. He's being held on 5 million dollars bond.
Police say the killing happened after an argument got out of hand.
The medical examiner's office says it appears that Koh had been stabbed.
According to Koh's Facebook page, he graduated from Glenbrook North High School in Northbrook in 2005 and attended Western Illinois University where he studied business.
Police have made no arrests but they stress the community is not in any danger.
"There's absolutely no threat to the community, and I think that's important to stress," said Chief Charles Wernick, Northbrook Police Department.
It was in the middle of the night when Northbrook police responded to a home at 1944 Birch Road.
Officers discovered the deceased body. The Northbrook Police Department is investigating the incident as a homicide.
Northbrook police called in the North Regional Crimes Task Force to investigate.
Neighbors say the family that lives at this home, this quiet home, they say a young man lives here with his mother and father.
"They're good people, they really are. I suppose the son supposedly had some issues, but they were good people," said Sharon Bergstein, neighbor.