The seemingly synonymous phrases for black-on-white random hate attacks on pedestrians, "Knockout Game" and  "Polar Bear Hunting," have both been around for awhile. I've tended to use them interchangeably. Yet, it turns out they are wildly different in popularity with the news media. From Google News:

• "knockout game" About 33,500 results (0.40 seconds)
• "polar bear hunting" 10 results (0.23 seconds)