"As soon as she was done the fan sitting next to me, a white middle-aged man, said that she 'sang too long' and that she 'N-worded it up,'" said Hennick, speaking with anchor Chris Cuomo on CNN's "New Day" Friday.
Hennick said he asked three times for clarification but the man remained defiant.
"'That's right and I stand by it,'" the man said, according to Hennick.
Shocked that anyone would use such language, and especially at a baseball game in front of his family, Hennick told an usher what happened and asked that he and his family be moved to different seats.
"Red Sox security jumped on it and took it extremely seriously," Hennick said, moving the family to a different seats and questioning the man about what he said.
What followed was an expulsion and lifetime ban from Fenway Park for the man who used the language, according to Hennick and an official statement from the Red Sox.
"During Tuesday night's Red Sox-Orioles game, it was reported to Red Sox security that a racial slur was used in a comment from one fan to another fan," the Red Sox said Wednesday. "The offending individual was promptly ejected from the ballpark, and has since been notified they are no longer welcome at Fenway Park."
Hennick said the incident did lead to difficult conversation with his son.
"My son very sweetly said, 'I thought it was over with white people and black people being separate,'" Hennick said. "I had to tell him that part of our past is history but these tensions still continue and some people are still very angry and this man seemed to be one of them."
On Tuesday, the Red Sox also issued an apology for racist behavior exhibited Monday night toward Baltimore Orioles outfielder Adam Jones, who said a fan threw a bag of peanuts at him and called him the N-word.