Maybe in a state that doesn't require that you have insurance, but in majority of other states it does not work like that once insurance is involved.
He rear ended another car, so his insurance needs to get involved no Ifs/buts about it. They can say 0 liability, but it will still be on your record (not to mention insurance costs going up slightly).
The accident also required police response. The accident, involving his car will now show up on cad for police databases.
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