Small trucking company – rear-ended by mechanic driving customer’s vehicle (fatality) – need legal direction

Location: Pennsylvania

I own a small trucking company and one of my drivers was recently rear-ended while working. The other driver was operating a customer’s vehicle from a mechanic shop at the time of the crash. According to the police report, he was traveling at a high rate of speed and was found at fault. Unfortunately, he died at the scene. We are very sorry for the loss of life. That said, our truck and trailer were damaged, and our business is losing income while the equipment is out of service. I’m trying to figure out the proper legal path forward and could use guidance from anyone familiar with commercial auto or trucking cases. Specifically: Should this be pursued through the vehicle owner’s insurance, the mechanic shop’s insurance, or both? What type of attorney should I be looking for (trucking accident, commercial auto, wrongful death defense, etc.)? If anyone can point me toward the right kind of lawyer or share experience with similar situations, I’d really appreciate it. Thanks in advance.