The incident, which was captured on video and uploaded to YouTube on Tuesday, begins with the officer calmly deploying the pepper spray at protesters, one of whom attempts to shield his face with a homemade sign.
Among the people hit by the spray is Anna Marie Stenberg, 69, a pro-Bernie Sanders protester from California. After being hit, she immediately turns from the fence and begins pouring water out of a bottle onto her eyes.
Stenberg was later arrested for climbing the 8-foot security fence surrounding the Wells Fargo Center, where the DNC was held. She was federally charged with entering a restricted zone and held for 20 hours.
According to SEPTA spokesman Andrew Busch, the officer deployed the spray because a Secret Service agent and a Homeland Security agent were both grabbed through the fence by protesters and hit with the metal gate.
Busch said federal authorities at that location sought the assistance of SEPTA police to secure the gate.
Before deploying the spray, the officer received permission from his sergeant, Busch said.
"We did interviews with the other agents involved and determined it was justified, and the investigation is concluded," Busch said.
All SEPTA police are outfitted with body cameras and the officer's camera footage was viewed during the investigation, Busch said.
Attorney Paul Hetznecker, who is representing Stenberg in her federal case, said he found it hard to believe there was a "thorough investigation" into the incident.
"Their investigation should be ongoing regarding the unwarranted use of the pepper spray because there is plenty of evidence that indicates, in respect to my client, that all she was doing was standing there and exercising her free-speech rights," he said.
Meanwhile, a federal magistrate judge on Friday released on bail two more protesters who were arrested after allegedly breaching the security fence outside the Wells Fargo Center.
Jeremy Graber, 31, of Woonsocket, R.I., and Travis Martin, 28, of Houston, face charges of entering restricted grounds, a misdemeanor punishable by up to a year in prison
They were among the 11 demonstrators U.S. Secret Service agents arrested on suspicion of either scaling the fence, which demarcated the security zone, or slipping through it after a protester cut a section of the barrier Wednesday night with bolt-cutters.
During an initial appearance in court Thursday, prosecutors suggested they would seek to hold Graber until his case was resolved because he was carrying three "throwing knives" at the time of his arrest.
His lawyer disputed that characterization, saying they were tools Graber used to cut gauze in his role as a medic.
On Friday, prosecutors dropped without explanation all objections to Graber's release. Neither side mentioned the issue in a brief hearing before U.S. Magistrate Judge Marilyn Heffley, and each declined to discuss it after the proceedings.