Based on your facts both parties could be found at fault. I agree, your friend needs to talk with a local personal injury attorney ASAP before talking to or making any statements to any insurance company.
DISCLAIMER: David J. McCormick is licensed to practice law in the State of Wisconsin and this answer is being provided for informational purposes only because the laws of your jurisdiction may differ. This answer based on general legal principles and is not intended for the purpose of providing specific legal advice or opinions. Under no circumstances does this answer constitute the establishment of an attorney-client relationship.
Usually the car coming from behind is at fault. However, since your friend's son was driving in reverse that generalization might not apply here. Your friend's son should talk to his insurance company. If he's hurt, he should talk to a personal injury lawyer. Avoid talking to the insurance company for the driver of the other vehicle.
Lawyers can't determine fault from a short Avvo posting. If he was injured, he should speak with a local personal injury lawyer, and if not, let the insurance company resolve.
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