The incident is said to have taken place in November 2019 at Wells Fargo Center. Police say the "investigation is active and ongoing with South Detectives Division."
Flyers season-ticket holder Chris Greenwell claims his son Brandon playfully patted Gritty on the head after a photo was taken, and that Gritty got out of his chair, "took a running start," and "punched my son as hard as he could," according to Christian Hetrick of the Philadelphia Inquirer.
Greenwell added that he took his son to a chiropractor about a week after the incident. Brandon was diagnosed with a "contusion to lower thoracic spine with subluxation" - or a back bruise - according to a document provided by the chiropractor.
The Flyers say there's no evidence to back up the accusation.
"We took Mr. Greenwell's allegations seriously and conducted a thorough investigation that found nothing to support this claim," the team said in a statement, according to the Courier-Post's Dave Isaac.
The incident was not caught on video because "cameras in that area of the center are focused on other locations," according to emails between Greenwell and officials at Comcast Spectator, the company that owns the Flyers.
Gritty gained instant popularity after arriving on the scene prior to the 2018-19 NHL season. The hairy, orange creature is arguably the most well-known mascot in all of sports.