This lady lived down the block from me
but I don't know either person.
She has since died of her injuries.
Beloved Broadway singing coach dies after hard shove in Manhattan
I'd recommend to the police investigating that they take a look at whatever scheduling system (hopefully pen-and-paper and not requiring passwords) this lady used, because the prosperous and generically, albeit fuzzily, attractive appearance of the murderer, strikes me as someone who might have taken vocal lessons from the coach.
Maybe the coach had some home truths about her future potential for success as a singer, and the woman didn't like what she heard.