That officer, Lt. Jonathan Josey, was suspended for 30 days with the intent to dismiss.
Action News has learned the union is holding that fundraiser for Josey on Sunday, October 28th.
A flyer promoting the fundraiser has the words "come on out and support one of our own."
According to the flyer, the event is $30 per person and includes "food, music, draft beer and well drinks."
The flyer was posted on the FOP's website and has the FOP logo at the top of the page.
"We are hosting and we are in complete, 100% support of the event and Jonathan Josey," FOP president John McNesby told Action News Friday.
Lt. Josey was fired even though the internal affairs investigation continues. Activists in the Puerto Rican community are blasting the FOP for holding the event at their headquarters.
"They should not raise anything for him. They're asking us as a community to be patient and they're asking us to wait until the investigation is over. And so we would think as leadership they would do the same," said Quetcy Lozada of the National Council of Puerto Rican Women.
The attorney for Aida Guzman,.the Chester woman Josey smacked down, says she is upset by the fundraising plan.
"It's sending a signal to the women of this city and to the community that it's okay to treat people this way, it's okay to viciously strike a woman like this, when she's not looking, in the face," said Enrique Latoison.
The video, posted on YouTube, showed Josey punching Guzman in the face. The incident happened after someone else threw a liquid at officers.
Mayor Michael Nutter has apologized to Guzman over the incident.
Nutter said week he had seen the video about 20 times and is "appalled," ''sickened" and "ashamed" by what happened.
The mayor formally apologized to the 39-year-old mother of 4 during a 20-minute closed door meeting.
"This was about a person, about a human being who has been injured in our city in a very graphic way, and I wanted to take a moment when the opportunity presented itself, to talk to her," said Mayor Michael Nutter.
Guzman's lawyer has said she is satisfied with what he calls the Mayor's heartfelt apology on behalf of the city, but he would not rule out a possible civil suit against Philadelphia.
Prosecutors have withdrawn a disorderly conduct charge against Guzman, but may consider possible charges against Lt. Josey.
The FOP is promising a legal fight to save his job and to provide lawyers to defend him if the District Attorney does bring charges.