I thought he was in the process of bringing propane tanks to the entrance to the building from his vehicle. The shootings could have taken place during that process.
Spokespeople for the PP clinic have stated that they have extensive security equipment in place and are working to find out why these features didn't keep this guy out or let staff know what was going on.
Like VIDEO CAMERAS. Where are those videos and if he was setting propane tanks outside the building, surely they would have noticed.
Besides, propane tanks are fairly recognizable and whatever he was carrying was described as mysterious.