A video posted on YouTube shows Lt. Jonathan Josey punching a woman in the face and knocking her to the ground before she is led off bloodied and handcuffed.
Earlier today, the Philadelphia District Attorney's Office said it intends to drop the disorderly conduct charge against the woman who was hit.
The woman was identified as Aida Gusman, 39, a mother of three and domestic worker, according to ABC News' Philadelphia station WPVI. She denied throwing anything at police and said she did not know why she was punched.
"I'm 40 years old. I don't have time to play games like that," Gusman told WPVI earlier in the week. In addition to her facial injury, she has cuts and bruises on her arm and hand.
The video was taken at Sunday's Puerto Rican Day Parade.
The video shows a crowd of blue-shirted police officers standing in the middle of a street, around a car. Someone on the left appears to throw something resembling silly string or a liquid on the cops. An officer in a white shirt rushes out of the crowd and goes after a woman with long, dark hair and a black T-shirt.
Her back is to the camera so it is unclear if she was saying anything to him. The officer appears to punch her in the face and then hit her in the back of the head. She falls to the ground where two officers apprehend her and lead her off. As she passes the camera, blood can be seen streaming down her face.
A fellow officer had called Josey, a 19-year veteran of the force, a "good cop."
"If I was in a jam, I'd want him backing me up," Lt. Ray Evers told ABCNews.com. "He's a good cop, but the video speaks for itself and the investigation will reveal whatever it reveals."
Josey, 39, has had 13 complaints made against him over his career, but Evers said that it is hard to quantify whether that is a lot, a little or average. He said it is not entirely unusual for officers who have frequent contact with people in rougher neighborhoods to have complaints made against them.
He said the 13 complaints against Josey range from verbal abuse to physical abuse.
"It's hard to decide if that's a lot or a little," Evers said. "Most were unfounded or not sustained."
The YouTube video, titled "Philadelphia Police Brutality" was posted on Sept. 30 and has been viewed over one million times.