Gunmen wearing Afghan police unfoirms killed 3 US soldiers, NATO said, according to the BBC.
An anonymous senior Afghan official told Reuters:
"During dinner, the police commander and his colleagues shot them and then fled. The commander was Afghan National Police in charge of local police in Sangin," a senior Afghan official told Reuters on condition of anonymity.
"It looks like he had drawn up a plan to kill them previously," the official said.
A NATO spokeswoman said they could not confirm if the incident was part of a larger insurgent infiltration, or if it was an isolated rogue shooting.
"All we know is that they were killed by an Afghan in a uniform of some sort," the spokeswoman said.
These kind of attacks are called green-on-blue shootings.
According to Reuters, there were 24 attacks last year that fit this description.
"We do our best, our intelligence departments try to prevent [the] entering of enemies into the Afghan National Army but [we] cannot promise that it will not happen again... I can't say anything about it, it is out of my control."