Charle Kirk assassination: was rifle staged ahead of time and is there video of people who could’ve staged it

The FBI published a picture of the potential shooter, but unless it was a short barreled rifle with a folding stock, he wasn’t carrying the rifle in the stairwell which means it was already on the roof. Since the FBI apparently has video of who was accessing the roof, they should review footage from that day and days prior to see who could be carrying a package that would hold the rifle they found.