Yes, it has been reported that his phone pinged as often being at the same locations as the victims for 2 or 3 weeks prior to the murders. And yes, it does appear that he may have been stalking his victims but don't forget, we have not seen any proof of that AND BK still has to be considered innocent UNTIL proven guilty, per the U.S Constitution.
In regards to BK breaking into their King Rd house, police have already said numerous times that there was no sign of forced entry so, technically, he did not break in......unless he was "that good" so as to not leave a sign or you know something I don't.