Original report: The 38-year-old firefighter intervened at 9:25 a.m., when police said the teens were harassing the couple in Manhattan's Upper East Side, WPIX reported.
According to police, one of the teens punched the firefighter, striking him throughout his body, the television station reported.
The man suffered a concussion and had five broken teeth, WABC reported. He also needed 25 stitches for his wounds, the television station reported.
Police released surveillance video that shows the teens, believed to be between 15 and 17 years old, smiling as they skipped down the sidewalk, WNBC reported.