How do we(35f) help our kids (>10m) process witnessing a deadly accident while on our family vacation?

Our family went on a road trip to a sporting event over the weekend and after the event finished, we were camping out watching the sunset when a man riding a street bike blasted down the highway and lost control right in front of us, launched off the bike and died of his injuries in the highway 50 yards from our campsite. I ran to try to assist and my spouse took the boys to another part of the grounds but they saw him crash and they knew it was really bad. Well, the road was closed for hours so they knew he died. They have been having trouble everytime we hear a motorcycle, they get anxiety and I am not sure how to approach further discussion without stressing them out. We talked several times and they both say they don't want to talk to a counselor but I just don't know, what is the best course of action?