NEWARK — An East Orange police officer who was off-duty but in uniform was arrested Wednesday morning, charged with assaulting a 20-year-old woman at a bus stop in Newark, then spitting on her, the Essex County Prosecutor’s Office said today.

The officer, Anthony Reed, 31, had just finished his shift and was driving his own car when he allegedly approached the woman on Stuyvesant Avenue and Abinger Place around 10 a.m., said Charlotte Smith, a prosecutor’s office spokeswoman.

The officer exchanged words with the woman, who was sitting at the bus stop, and who authorities said he had never met. Reed then got out of his car, grabbed her, pushed her to ground and spit on her face, police said.

Authorities are investigating what prompted Reed, who has been on the force for two years, to approach the woman in the first place.

Newark police arrested him at the scene. He was charged with attempted aggravated assault, and bail was set at $75,000. Newark police and the Essex County Prosecutor’s Office is still investigating.

East Orange police Sgt. Andrew DiElmo said the department’s own professional standards unit is also looking into the incident.