The killing of a New York City police officer working in a plainclothes unit has drawn attention to the dangers of a crime-fighting force that by design usually goes unnoticed.

Officer Brian Moore died after he was shot last weekend in Queens by a man he stopped because he suspected he had a weapon.

Moore was among hundreds of plainclothes officers believed to be on the streets. They conceal guns and badges to spot criminals who otherwise might behave around uniformed officers. They are among the department’s roughly 20,000-officer patrol force.

Sometimes, the units have been criticized, like after four white officers in a plainclothes anti-crime team fired 41 shots and killed a Guinea immigrant more than 15 years ago.

(AP)