There is no report that states victim was walking towards truck. There is no mantion in any press release, or news report (including this one) of the victim walking towards the truck. It is clearly stated on several occasions where MB entered the building and that she walked towards where they believe the suspect to have been at the time.
I have read everything of relevance to MB's entrance that our awesome sleuthers have posted (SW, LE statements) and reviewed the images posted (thanks batbrat for the color coded awning image!). I have yet to see anything that makes this a closed case. Much like everything else in this case, I still see all popular theories as viable. After the last 20 pages or so on this topic, I am still firmly on the parked at PC, walked to main west side entrance, turned right, walked to SW corner, killed in SW corner, before getting the PC door unlocked. That being said, others have proposed scenarios that would work as well and fit the facts we do have. We can argue what LE meant by awning or main, but unless someone has other LE or SW comments not recently posted, both scenarios are possible. Ditto with the key speculation. We can say it is "likely" one key would have opened all outside doors but we really have no clue at this point. I have actually had the opposite experience with access to large buildings, but that gets me no where with knowing how this church was keyed.