You're right, we don't know. But this is all my speculation. However, in rethinking this, the last LE saw MB was when she was headed down the hallway in the vicinity where SP was last seen on the tape by LE. We know through our VI that she was murdered in the junction/corner of the north and west hallway where cameras were not operational. If that is true, imo it appears that SP was not in the auditorium at the time MB arrived in the building and was waiting for her somewhere near that corner. LE did not see MB or SP again after MB was viewed walking down the hallway. LE has said the murder and aftermath was not on tape. LE also said they thought SP escaped the way he came in...through the kitchen.....which was steps away from where MB was murdered. OK, I don't know about anyone else but I've just now convinced myself this was definately not an accident, this was not a burglar who happened to bump into MB unexpectly,, this was someone who knew she was coming down the hallway, and was ready to assassinate her. All just my opinion and speculation.
Yeah, your speculation (and arbitrarily seeing the evidence in a way to fit it) offers an idea that is certainly possible. Unfortuntately we just don't know enough about the worthless perp, or have any objectively differentiating evidence from the murder, to say with any certainty what that loser's intent must have been.