( CNN ) -- A U.S. serviceman was among six victims of an early morning shooting at a Ciudad Juarez , Mexico , strip club Wednesday , officials said . Unidentified gunmen entered the Amadeus club in the border city across from El Paso , Texas , just after midnight and fatally shot six men , Chihuahua state attorney general 's office spokesman Arturo Sandoval said . An additional person was injured , he said . Two of the victims were identified as employees of the strip club , a waiter and a security guard , the spokesman said . Another was identified as an American citizen and member of the U.S. Air Force , Sandoval said . A statement from Holloman Air Force Base , near Alamogordo , New Mexico , confirmed that the airman was based there , and identified him as Staff Sgt . David Booher , 26 . The gunmen appeared to have targeted the victims , Sandoval said . `` Everything indicates that these people were looking for these men , '' he said . Investigators recovered more than 30 shells from the scene . Because of drug-related violence , particularly in border cities , Juarez is considered off-limits for the U.S. military . At Fort Bliss in El Paso , for instance , a memorandum prohibits its soldiers from traveling into the Mexican state of Chihuahua , where Ciudad Juarez is located . More than 2,000 killings have been recorded in Juarez this year . CNN 's Mayra Cuevas-Nazario , Mike Mount , Dave Alsup and Mariano Castillo contributed to this report .
Air Force Staff Sgt . David Booher shot with 5 others in Ciudad Juarez . Gunmen appeared to have targeted the victims , Mexican spokesman says . Juarez is considered off-limits for the U.S. military because of drug violence .