TMZ Sports spoke to an official from the Metro Nashville Police Department, who confirmed Matthew Havel filed a simple assault report.
Twitter user Cooper Stefaniak shared a video of the altercation on Twitter:
Havel spoke to Bleacher Report's Joon Lee about what preceded the incident.
"We didn't say anything like, 'You guys are bad coaches,'" Havel said. "We were sitting there for an hour, hour-and-a-half, talking, and then it wasn't with them, it was with the son and the nephew. Then we had pictures of Matthew's championship ring on my wife's hand. You don't let that out of your hand for anybody."
A source, however, told Lee that Rex was growing agitated as a result of "heckling from the uninvited guests."
Rex most recently was the Buffalo Bills' head coach, with Rob the assistant to the head coach for defense. Both were fired after the team started the 2016 season with a 7-8 record.
In April, ESPN hired Rex as an NFL analyst.