If the Tarot shooter was of student age, the backpack theory would work well. Most AR-15 variants will break down into upper lower sections pretty quickly that would easily fit in a backpack.
The backpack would be incongruous with the guy in a deliver uniform.
My point with the graphic was to illustrate that anything is possible and everyone should keep an open mind.
He's 25-30, dresses like a college student which gives him a wide range of clothing compatible with his mission...and has a back pack. He may even be living in a dorm...goes back at anytime and no one cares.
Look for a guy who looks like the scenery.
Sac