A group of Orthodox Jews in Queens, N.Y., has decided to learn how to defend themselves from the rumored “knockout” game. A group of about 30 people, aged 16 to 62, gathered in the basement of Young Israel of Queens Synagogue in Kew Gardens to learn the basics of Krav Maga, the Israeli Defense Force’s martial-arts system, according to a New York Post report.

In addition to teaching the basic techniques, Avraham Avramcheyiv, the instructor, advised the class to be aware of their surroundings, in order to avoid being taken by surprise by attacks. “People these days are naïve and unaware of what’s going on around them,” Avramcheyiv said. “The most important thing to focus on is being aware of your surroundings.”

Henry Mosovic, the oldest person in the class, told the Post that he was frightened by knockout. “People should be aware of it. I know some men and women got hurt pretty badly,” he said.

New York City police commissioner Ray Kelly said last month that the NYPD is investigating the issue. “We’re trying to determine whether or not this is a real phenomenon,” Kelly said. “I mean, yes, something like this can happen. But we would like to have people come forward and give us any information they have.”