Primary rental car insurance follow up.

I was in an accident in California in July. The police did not assign fault despite what I thought was a clear case of the other driver not following the rules. After a month or so, the claim was completed and the insurance paid for the damage to the rental car. I never heard anything from the other driver. Note that airbags did not deploy but the other driver chose to go to the hospital. My family and I did not.

Just this week, I received a poorly punctuated threatening letter from an attorney about a “claim” from the other driver. He says he will sue and that I need to send over my insurance information. My question is whether I refer them to Capital one’s insurance or if I have to give them my own insurance?

Feels very ambulance chaser to me but it is stressing me out.