A series of punching attacks -- including one against a 12-year-old Brooklyn boy -- are being investigated by the NYPD to determine if they are part of a violent behavior known as the "knockout game."

The attacks, in which strangers punch unsuspecting victims, have been reported by police in other parts of the United States and England. Tuesday, NYPD Commissioner Ray Kelly said eight attacks in the city were being reviewed.

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A series of punching attacks -- including one against a 12-year-old Brooklyn boy -- are being investigated by the NYPD to determine if they are part of a violent behavior known as the "knockout game."

The attacks, in which strangers punch unsuspecting victims, have been reported by police in other parts of the United States and England. Tuesday, NYPD Commissioner Ray Kelly said eight attacks in the city were being reviewed.

In remarks to reporters, Kelly was careful in characterizing the assaults and wouldn't say definitively that they were motivated by the knockout game.

"The press calls it a 'knockout game.' We don't discount that possibility. We continue to investigate," Kelly said.

Several attacks this month may fit the pattern -- sudden assaults on a victim by a stranger on the street without provocation. The assaults have been clustered in Brooklyn's Crown Heights area and Jewish people have been the targets, said Rabbi Yaacov Behrman, executive director of the Jewish Future Alliance, an advocacy group.

"It means basically Crown Heights is ground zero for knockout," Behrman said. He reported a heavier police presence in the area since the attacks became noticed.

Four or five of those assaults are being reviewed as possible knockouts, Behrman said. He noted that two other assaults this month are being studied as possible bias attacks. In those, Jewish people were punched by African-American males, he said.

Kelly said that the latest attack occurred Tuesday in the Flatlands section of Brooklyn. There, an elderly woman in her 70s was struck by a man with whom she appears to never have had any previous contact. The woman was treated in a hospital and released.

"Whether it is part of this so called knockout, we are still trying to determine," Kelly said.

He also said detectives arrested a 13-year-old for striking a 12-year-old with a ball.

To give perspective, Kelly said each attack may have elements that remove it from the knockout category.

"Sometimes there is more to it than just an individual going up to someone and punching someone," Kelly said.