Call the police and continue to be a witness. Do not intervene. You are not LEO. Unless you are protecting yourself, or your family or an active shooter situation like a Columbine, you have no right or responsibility to intervene.
Don't take this the wrong way but your carry permit does not make you LEO, a super hero, or responsible for the world's problems.
You are much more likely to get yourself into trouble trying to "help" in this type of situation than you are to actually render aid.