The confrontation erupted in the 12th minute of stoppage time when Cavan's older brother and team-mate, Quinn Sullivan, went down inside the 18-yard box. Inter Miami defender Ian Fray appeared to step over and then on Quinn, who took exception to the extra physical contact.
After Quinn body-slammed Fray in response, Cavan entered the action nearby to defend his sibling as things rapidly escalated between both teams. Cavan and Miami midfielder Yannick Bright began pushing and shoving each other as team-mates intervened.
Once calm was restored after referee discussions, both Cavan and Bright were presented with red cards, while Quinn received a yellow card for his role in the fracas.