A pack of young teenage girls randomly attacked an elderly man on a Brooklyn subway platform early Monday — with at least one assailant whacking the victim with a scooter, cops and police sources said. The 76-year-old man was lying on a bench at the Rockaway Avenue subway station when the five suspects launched the assault, punching and kicking his head around 2:10 a.m., according to authorities. One of the perpetrators even swung her scooter at the man’s head in what sources said was an unprovoked attack on northbound C line platform. The offenders are believed to be between the...