Dog leaked fluid out of butt?

We just got a 6 month old German shepherd puppy male from a couple who said they didn’t want them anymore. We already have a 8 year old German shepherd, they get along pretty okay. I took them both on a walk with my friend. The puppy walked on the opposite side of a mailbox so they he leash was gonna get caught. I quickly grabbed around the mailbox but the length of the leash smacked into the metal and made a loud clang. Scared the puppy so bad I calmed him down but then I looked at his butt and tail it was getting soaked I thought he was peeing on himself. I’m assuming this may be anal glad fluid? My other dog rushed over and started licking him clean and would not stop. He seems to be fine today I wiped him off and all. My question is, was it anal glad fluid, is that normal and will he be fine? 😭 I feel so bad