Authorities were called out to a report of a domestic argument at a home on the 100 block of Rancocas Road at around 3:15 p.m.
It is not clear what occurred next, but soon an arriving female officer and a man from the home wound up outside in the backyard.
At that point, police say the male lunged at the officer with a knife and she shot him.
"All we heard were gunshots and we ran out; I thought somebody had hit my car," neighbor Maggie Mobley said.
The male was taken to Helene Fuld Medical Center in Trenton; he is said to have suffered a non-life-threatening injury.
Family members of the male say he was shot in the abdomen.
Though the police officer was shaken up, she was not hospitalized.