(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.
What is considered off-limits? where is ciudad juarez How many people were shot? who is the Mexican spokesman? what kind of violence is there what is considered off limits what did the gunmen do Who shot 5 in Ciudad Juarez? where was sgt david shot Is anyone off limits? Who is considered off limits? what is considered off limits Who was shot along with 5 others? Gunmen appeared to have what?
Juarez Mexico, six Arturo Sandoval drug-related Juarez fatally shot six men, Unidentified gunmen Ciudad Juarez, Mexico, Juarez is considered off-limits Juarez Juarez Staff Sgt. David Booher, targeted the victims,
question: What is considered off-limits?, answer: Juarez | question: where is ciudad juarez, answer: Mexico, | question: How many people were shot?, answer: six | question: who is the Mexican spokesman?, answer: Arturo Sandoval | question: what kind of violence is there, answer: drug-related | question: what is considered off limits, answer: Juarez | question: what did the gunmen do, answer: fatally shot six men, | question: Who shot 5 in Ciudad Juarez?, answer: Unidentified gunmen | question: where was sgt david shot, answer: Ciudad Juarez, Mexico, | question: Is anyone off limits?, answer: Juarez is considered off-limits | question: Who is considered off limits?, answer: Juarez | question: what is considered off limits, answer: Juarez | question: Who was shot along with 5 others?, answer: Staff Sgt. David Booher, | question: Gunmen appeared to have what?, answer: targeted the victims,