I pretty much explained it earlier. There are spy networks using people like this. The idea is that, "anything that hurts the US. is good for us."
But this one was too notorious, and yes, I'm pretty sure he wanted to do it, and they agreed to help him do it if he would use casino chips to make pots of money for agents, or planes for moving them around, let alone just using the casinos to launder ill gotten money through.
They were all there right with him until he started shooting, they jetted out because it was tied back to them and it probably started a war. All those guns you see laying around, and it is admittedly a lot of guns, were theirs, that were left because of the way they were purchased and distributed (they could not be removed.)
All the equipment was probably bought using a process that makes it really hard to detect until the event has passed. It was probably done using a small rubber band segment.
There was even a woman going around supposedly telling people at the concert to get out of there beforehand, but of course, it's the nature of the future to not understand the importance of following somebody's vague assertions until it was too late to do anything about it.
It appears the whole incident had very negative connotations in the gray tech area, with people using the tech even thinking it was too much, and trying to intervene.
Once again, please un-fund ATF and FBI and send money to me who can work out stuff like this that they refuse or are unwilling to acknowledge.