Think about what you were taught (if anything, as most truly professional educators who stay current in their field stopped this technique years ago) about the sternal rub in school? What is the purpose of it? Now, with that purpose in mind, is there any medical indication for a good Samaritan to perform it? And if not, can it be legally justified? And if not, is that not assault (or whatever term your jurisdiction assigns to non-consensual bodily contact)?
Noxious stimulus is not a therapeutic modality. It is a diagnostic assessment tool. And anyone who doesn't clearly understand that shouldn't be performing it in the first place.
Did he call 911? If not, then is that because he felt she didn't need medical attention? And if he felt she didn't need medical attention, why was he attempting to render it? Sorry, but this whole scenario just comes across as completely inappropriate on multiple levels.