MarkS shared some good info.
I am a police officer in Texas. Though a different world than Cali some things will still be the same.
Like MarkS said a parking lot is private property. That means no citations and many times no accident report at all. Here we don't have to do an accident report for people and can let them report the accident to the state themselves, and that's if they want. It is always perfectly fine to just exchange information and go your separate ways, only reporting it to the insurance companies, or settling whatever way the two parties see fit. Too many people believe you must get an accident report.
I wasn't there so I don't know exactly what happened but Im not so sure the people following you broke any law by blocking you in. Even on private property you are to stop and give information in the event of a collision. Failing to do so can be an FSGI. If the car truly believed you were trying to flee they could have had ever right to follow you and block your car. If you had done nothing then it would be a whole other matter but from the limited info I have Im not sure they broke the law by blocking your vehicle. Again, I was not there but don't freak out and take a bat to their car as mikesmelly said they would do.That will just get you shot or run over. It sounds as if you handled it as well as you could and the more calm you are the more the police will be willing to help you. We deal with crazy drama all day long so its nice to be able to deal with people with a level head from time to time.
As a police officer you get very good at picking out new damage from old and putting together how the damage was caused. You can see the direction the two cars were going when they hit and very rarely need much help in getting things sorted as to who was at fault.
You should be getting a call from both yours and theirs insurance companies. Be very careful when talking to theirs and if at all possible let your company handle all dealings with them. They will try to rope you into saying things to place blame and everything will be getting recorded. If the other party really is just out for money don't be surprised to hear they went to the hospital or doctor and have some sort of injury.
Good luck.