Philadelphia Mayor Michael Nutter and other city leaders say they won't tolerate a deadly "knockout game" in their city, in which teens approach strangers and try to knock them out with just one punch.
The attacks have happened in several states and in England, and have resulted in at least two deaths.
Nutter said that anyone caught participating in the attacks will face a minimal charge of aggravated assault. He also indicated "game" players could face serious charges of third degree murder if caught.
His warning is the latest example of political leaders and law enforcement who are fighting back against the deadly attacks.
"You're also hurting another human being for no reason at all. There's no excuse for this kind of behavior, it will not be tolerated here in the city," Nutter said.
"We will do everything we can to both prevent, but if someone does engage, we will catch you. You'll be prosecuted, and your life will be changed dramatically," he said.
Some reports raise questions on whether the attacks are racially motivated. In some cases, black teens have participated in the attack games. Others point out that many of the assaults have been against Jews.