I work for the police in the UK and this is a real regular occurrence sadly.
It's more than likely an attempt at an insurance scam, whereby the occupants claim you were at fault and all suddenly end up with whiplash (or whipcash as it's also known).
I don't know the highway code in North America, but here, if you hit the rear of someone else's vehicle, you're pretty much always at fault in the eyes of the insurance companies. Even if the other person reverses in to you, the insurance companies log it as you hitting the other vehicle. It's a joke to be honest.
If no damage was caused, then you got real lucky and those jerks will have left disappointed. But it is big business. Some groups in the UK have been caught doing similar things many, many times and making tens of thousands of pounds from it.
If (when) they eventually get caught, they can often serve some time as a result.
My advice is, if you ever feel like it's not right, get as much detail as you can. Names/VRM/Make& Model/Descriptions of drivers/Photos of cars and even if possible, photos of all the occupants. It's not uncommon that all of a sudden, the car was full of their family members too, even when there was only actually two people involved.
Quick one on installing cameras in you cars: Make sure you let your insurance companies know. Often there's a clause that if you're insurance company doesn't know you have it, it can be declared invalid in an insurance claim. Which is just another way of them avoiding making a pay out.