An NYPD officer serving in the U.S. Air National Guard has been killed in a suicide bombing in Afghanistan, Police Commissioner Bill Bratton said Monday night. 

Detective Joseph Lemm was among six U.S. troops killed at the Bagram air base. 

Bratton said in a statement that Lemm "epitomized the selflessness we can only strive for: putting his country and city first." He said Lemm, a 15-year veteran of the NYPD, was promoted to detective in January 2014 and had served in the Bronx Warrant Squad. He had been deployed three times to serve in the military overseas. He leaves behind a wife and two children.

"Tonight, we grieve and we remember this selfless public servant who dedicated his life to protecting others,” Bratton continued. 

Gov. Andrew Cuomo directed flags to be flown at half-staff Wednesday on state government buildings.

"Staff Sgt. Joe Lemm served this nation with the selflessness and bravery that embodies the U.S. Armed forces and the NYPD," Cuomo said in a statement. "On behalf of all New Yorkers, I extend my deepest condolences to his family, friends, fellow officers and service members."

The White House expressed its condolences to the families of the six troops and said the United States remains committed to supporting the Afghan people and their government.

"Our thoughts and prayers are with the victims, their families, and their loved ones," the White House said in a statement.

The six Americans were killed when a suicide bomber on a motorbike struck their patrol near Bagram air base, a U.S. official said, in the latest high-profile attack claimed by Taliban insurgents.