Philadelphia police said Wednesday that they are investigating the alleged physical assault, which happened in November 2019 at the Wells Fargo Center.
Chris Greenwell told Action News that his son tapped the mascot's head after the photo which prompted Gritty to lunge out of his chair and punch the boy in the back.
The family said the teen was hit so hard, he required medical attention.
In a statement, the Flyers organization said it took the allegations seriously and conducted a thorough investigation, but "found nothing to support this claim."
Further details surrounding the assault were not immediately available.