This is an example of sympatric speciation, because there is no geographical isolation of those groups. A nice trick to remember this concept is to look at the etymology of the word:
sym (from greek: together) + patra (from greek: fatherland)
Therefore, it make sense that every time we are talking about a group which splits into two differents species coexisting in the same "fatherland" (we use this word because there is no geographical barrier between them), we refer to sympatric speciation.
Since the species developed different social behavior, as the stament of the question remarks, the isolation mechanism operating here is: behavioral.
