DNA Matching: Mystery Second or Third Cousin

My third cousin, R.S., has a new closer cousin in his DNA matches at 23andMe.  They share 1.37% over four segments.  They are likely second or third cousins, though the prediction of the site is second through fourth cousins.

Second cousins share a pair of great grandparents, while third cousins share great great grandparents.

Let's hope that this person responds to my request to communicate.  Absent an adoption or non-paternal event, we should be able to figure out the connection.

Relative Finder top genetic matches for my third cousin, R.S. at 23andMe.
This mystery person could be a closer match than my father and R.S.