The cops were called. And I don't see how you can claim that the assault was foreseeable to the owner.I doubt seriously McDonald's employees are trained or required to break up fights.
LOL, there is a big difference from breaking up a fight and filming it, cheering the beating on, instigating it and warming the perpetrators of the cops!
By law businesses owe have certain duties to their patrons. They have a duty to protect (its different for another patron's duty to the victim - they could sit there and do nothing). The duty to protect includes against battery.
The elements of the duty to protect are something like this:
1. The owner (who is vicarious liable for the actions of his employees who are under his control - not independent contractors) had a duty to exercise reasonable care to protect his/her patron from harm or assault - I think not filming, instigating the fight, cheering the beating and warning the perpetrators is unreasonable
2. The owner failed to exercise reasonable care to protect his/her patron no doubt see above
3. The assault must be foreseeable to the owner. No doubt this one was
4. The assault occured on the owners premise which he owns and controls . It all took place in the McDonalds
5. The owner's failure to exercise reasonable care caused the resulting injuries/death Seizures at the end are good proof. Injury can be a fear of the public
This won't make it to court.
An assault happening in your establish is foreseeable!