Members of the Philadelphia Police Department arrive to shut down the Occupy Philadelphia tent encampment near City Hall in the early hours of November 30, 2011 in Philadelphia, Pennsylvania. The protesters had defied a previous deadline to vacate the encampment. (Photo by Jeff Fusco/Getty Images)

Civil rights activists and community groups in Philadelphia are scheduled to participate in a rally Thursday seeking justice for a teenage boy who claims he was brutally assaulted by a female police officer.

Darrin Manning, 16, says he was subjected to a violent pat down that resulted in serious injuries to his genitals. He was forced to undergo emergency surgery and doctors warn he may never be able to father children.

At a press conference Friday, police commissioner Charles Ramsey said Philadelphia police have launched an internal investigation. He said the department was taking the incident “very seriously,” and urged potential witnesses to come forward.

The incident happened on January 7 when Manning, 16, was on his way to an after-school basketball game along with a group of teammates near 15th and Girard Street. Police say one student caught police attention and the boys scattered as the officers approached.

Manning, who was still wearing school uniform, says he was handcuffed and subjected to a violent pat down by a female police officer who grabbed and pulled his genitals so hard it ruptured his testicle.

“She patted me down again, and then I felt her reach, and she grabbed my butt,” Manning told a local TV station. “And then she grabbed and squeezed again and pulled down. And that’s when I heard something pop, like I felt it pop.”

Lewis Small, Manning’s attorney, said, “It’s horrible. It’s sexual assault, as far as I’m concerned.”

Medical records show Manning endured emergency surgery at Children’s Hospital of Philadelphia the following day. Doctors say his injuries could be permanent and the teen may be left infertile. Manning is still having trouble walking and is in a wheelchair.

The straight-A sophomore at Mathematics, Civics & Sciences Charter School in Philadelphia has been charged with resisting arrest and aggravated assault.

Police records show that Manning fought with officer Thomas Purcell. Manning spent eight hours in jail, and police say he never reported any injuries.

The teenager, who has never been in trouble with the police, says he didn’t do anything wrong. “I didn’t deserve to be wrongly stopped,” Manning said. “They didn’t – they didn’t tell me what I did.”

At the press conference Ramsey played surveillance video of the incident but shied away from drawing conclusions on the arrest pending further investigation. “We want to piece together what happened,” he said.

The surveillance video shows children running down Girard, Manning among them. It is difficult to tell exactly what happened during Manning’s arrest.

Police Commissioner Charles Ramsey said the boy and his family have not filed a formal complaint or spoken to police.

Follow Kunbi Tinuoye on Twitter at @Kunbiti