Seriously though... the best thing to do is pull over (assuming the perpetrators have gone or you have passed the area where they were), and immediately call the police to report it. If they were in a vehicle, then describe the vehicle as well as you can, and tell the police which direction it was headed. If the perpetrators were on foot, describe them as best you are able, and the exact location the incident happened.
You may think initially that the police won't catch up with the perpetrators, but people who perform these acts usually don't stop with just one person. If the police see someone in the vicinity who matches your description, your report may save someone from being assaulted as well. It's well worth it for everyone.
no subject
*begin snark*
Don't ride a bike.
*end snark*
Seriously though... the best thing to do is pull over (assuming the perpetrators have gone or you have passed the area where they were), and immediately call the police to report it. If they were in a vehicle, then describe the vehicle as well as you can, and tell the police which direction it was headed. If the perpetrators were on foot, describe them as best you are able, and the exact location the incident happened.
You may think initially that the police won't catch up with the perpetrators, but people who perform these acts usually don't stop with just one person. If the police see someone in the vicinity who matches your description, your report may save someone from being assaulted as well. It's well worth it for everyone.