Having witnessed a food fight at the Morris Center at BYU when I was a freshman many years ago (the culprits waited until me and my room mate had moved from ground zero to visit the potato bar before they let loose), I don't think I would consider it a prank... funny and juvenile and disgusting all at the same time and perhaps on the level of vandalism, but certainly not a prank. I don't believe BYU ever positively ID'd the culprits (well, cuz they were from my dorm floor and I think I ended up seeing all the guys from the floor in the MTC several months later that fall)
Not dismissing the seriousness of the incident, but I wonder if it would be getting as much attention and fallout if a police officer had not been injured in the aftermath. You have one instigator charged with felony resisting arrest, another with probably inciting a riot and disorderly conduct, and another with assault. Why not some vandalism and destruction of property too?
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It seems to me the only thing you've learned is that Caesar is a "salad dressing dude."
Seems a bit excessive to me. I have no problem with making them clean the mess up and some other forms of school punishment. They should also have to pay for any damages. It's not like it was a real fight. Of course, I wasn't there. Maybe it got so out of hand that the charges are warranted.