If you saw a father punch his son in the mouth at the grocery store. What would you do?
I came up to him and said "If your in the mood to hit someone I'll be at the gym at 4pm bring your boxing gloves. Otherwise leave the kid alone." He didn't show up. But the store owners were more then accommodating in supplying the security tapes to the police. Along with the licence plate I happened to write down as the guy drove away.