"It was instant, I was, like 'Oh my God, call 911, this is bad'," Russell told KOAM. "I'm not even sure exactly how it happened at this point ... but ... yeah ... it was scary."
An ambulance took Gregg to an area hospital, and then he was transferred to the University of Kansas Hospital, the television station reported.
Surgeon Koji Ebersole said Gregg was fortunate the knife stopped before it hit his artery.
"It could not have had a pound more force on it and him survive that event," Ebersole told KOAM.
Doctors were able to remove the knife, and Gregg is now recovering well, doctors told "Inside Edition."
"It's almost a miracle, it's amazing," Russell told the television show. "How it happened was one in a million."