Mayor Nutter, hoping to forestall the spread of random assaults and the so-called knockout game in Philadelphia, urged youths and parents Monday to consider the consequences of such attacks.
"First and foremost, this is disgusting and inexcusable behavior," Nutter said at an evening news conference at City Hall.
"And it's not a game. You can seriously injure, possibly even kill, someone with this kind of activity."
He vowed that anyone caught participating in "this current rash of stupidity" would be caught and prosecuted.
A perpetrator who might otherwise have a clean record could suffer repercussions that "can last a lifetime," Nutter said.
He cited reported instances of random attacks in New York City, Chicago, Pittsburgh, San Diego, St. Louis, Hoboken, N.J., and, he added, "possibly here in Philadelphia."
On Nov. 11, a 29-year-old man was assaulted by several males at a pizza shop in the 7900 block of Verree Road in Fox Chase.
Police Commissioner Charles H. Ramsey said two juveniles had been arrested and charged with the attack.
Although police previously described the incident as an example of the "knockout game," in which teenagers approach strangers and attempt to knock them unconscious with a single blow, Ramsey said at Nutter's news conference that the two defendants "did not confess that this was part of a knockout game."
Ramsey said police are reviewing cases for evidence that recently reported assaults may have been random.
He also said police are watching for signs of racial, gender, or other hate motivations. He noted that the victim and the alleged assailants in the Fox Chase assault were all white.