Vehicle accident while at work, which insurance pays

Husband was at work, on the clock, in a work vehicle and on work property. He was involved in a minor accident with a visitor to the workplace in their personal vehicle. Police report was taken at the time of the accident, along with incident reports by his employer. Now he’s getting letters from the other driver’s insurance and lawyers demanding that he contact them.

Is this handled by his employer’s insurance only, or does he have to notify our personal auto policy of the accident so they can get involved?