Memphis mob attack part of "knockout game" trend?

Ten teenagers and one adult are under arrest after a brutal mob attack at a Memphis grocery store.

And at least one witness said the teens appeared to be playing the so-called "knockout game," CBS News correspondent Don Dahler reports.

It's unclear if this was gang-related or had to do with the knockout game, or both, but the violent game has become increasingly popular around the country. The goal: to hit unsuspecting strangers and knock them out with a single punch.

According to police, the mob started beating a customer as he got out of his car in the store's parking lot.

Investigators say that when two employees came to help, the teens attacked, kicking them until they lost consciousness.

A witness said some of the kids threw pumpkins at one of the unconscious victims.

"It didn't seem real," a witness said. "It didn't seem like any of that would happen."

The witness, who asked not to be identified, said this was part of a violent game.

"They were playing a game called 'point them out, knock them out' where they would point someone out and attempt to knock them out or fight them. There was no real reason behind it," the witness said.

Suspected cases of "knockout game" have been popping up around the country.

In Pittsburgh, an unsuspecting teacher was hit so hard, he fell headfirst into the curb. In addition, last month in New York, a 72-year-old man was knocked to the ground in the middle of the day for no apparent reason.

Police have not revealed a possible motive in the Memphis attack, but the city's mayor said this kind of thing won't be tolerated.

"We're not going to accept this, 'Well, they didn't have anything to do so they went out and formed a mob.' That dog will not hunt in Memphis, Tennessee," Mayor A.C. Wharton said.

While the video appears to show black teens attacking a white victim, that witness said some of the victims were black and that the mob was a mix of races. Police have not said the violence was racially motivated.