An internal New York Police Department review has found an officer violated department guidelines when he used pepper spray on Occupy Wall Street protesters last month, a source with knowledge of the investigation has told the Associated Press.

Deputy Inspector Anthony Bologna faces losing 10 vacation days after the incident on 24 September incident near Union Square, shortly after the protests began in lower Manhattan, the source said.

Video from the protests shows a small group of mostly women corralled by orange netting used by officers to control crowds. Bologna approaches and seemingly without warning blasted a cluster of women with pepper spray. Two of the women crumple on the sidewalk in pain. One screams.

The incident sparked outrage by demonstrators and a collection of online gawkers who were watching the protests. It also helped propel the movement into the national spotlight.

Video has played an important role in the demonstration in New York, with police and protesters carrying cameras in every encounter.

Bologna, who works in upper Manhattan, may choose to appeal the decision. A call to his union spokesman wasn't immediately returned on Tuesday. But the union earlier had said Bologna's actions were motivated by his concern for the safety of officers under his command and the safety of the public.

Shortly after the incident, a hacker group Anonymous affiliated with the Occupy Wall Street movement posted on its website Bologna's address, his phone number and where his children went to school, among other personal details. Police department officials said that was out of line and deplorable.

Pepper spray is relatively low on the spectrum of force available to officers. The patrol guide lists several situations where an officer may use it, including to protect him or herself. The guide prohibits the use of pepper spray against subjects who don't actively resist.