"Paddock, who had rigged cameras in the hallway and on the peephole of the door, saw Campos coming and fired through the door, hitting him in the leg, "
This is clear evidence of he had it seriously planned out.
“rigged cameras in the hallway and on the peephole of the door”
Someone posted a schematic of the suite and area around it. One of the doors to the suite was at the dead end of a long hallway. I assume that’s where he had the peephole cam. If so, he was able to see anyone coming for a very long distance.
And I think the other suite door, which was around the corner, was across from the stairwell.
Someone did some intricate planning.