>Maybe he wasn't just told to stand down, but he was told to let a particular somebody without approved access in.
I'm sure he was told to be on the lookout for their patsy (Cruz) and take him down, and if he heard gunshots to stay away. If he got within sight that the trained military operator/contractor (real shooter) was informed to shoot him dead.
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Just a guess based on the administration's history of covering up mass shooting events like Las Vegas.