And what the hell is a tight brake? Actually never mind, because it doesn't matter. But seriously... what's a tight brake? Anyway...
Unless you were injured AND covered for no-fault accident benefits / personal injury protection under your personal policy, your own insurance company will have nothing to do with this accident.
Your employer owns the vehicle you were driving, so this accident is 100% their problem. They'll ask you to provide whatever information you have, and they'll let you know if they have any other questions. And they probably won't have any other questions, except for checking in with you to make sure you're okay after the crash.
You were rear-ended, which means the accident was 100% the other idiot's fault. There is no such thing as a rear-end collision that is even partially the fault of the vehicle in front, so you have nothing to worry about. Even if you suddenly jumped on the brake and locked all 4 wheels for no reason at all, it's still the other idiot's fault for following too close behind you.
The owner, not the driver, is always responsible for their vehicle and whatever damage it causes or receives. That's what the law says in every state, territory, province, island fortress and everywhere else in the civilized world. If the owner (your employer) gave you permission to operate their vehicle, they also gave you permission to have an accident with it. Don't feel bad for them, they knew the risks when they handed you the keys.
In other words, you have no responsibilities here whatsoever. Your employer and their insurance company knew this might happen, and they're totally ready for it. All you need to do is a) give them whatever info you have about the crash and b) get into a warm bath (with or without fragrant bubbles, your choice) and relax. Being in an accident, even a minor one, can be really stressful.