Also, what made them think they had an armed shooter?
As opposed to an unarmed shooter?
Frankly, they've got cameras for a reason. If they can't verify where the guy went, they need to rework their camera coverage ASAP, and flog whoever wasted the money on the existing system.
Why wasn't there someone available to talk to him, at least to the extent of saying the school would not comment on security measures? They're probably supposed to refer him to district staff at another location, but the principal or vice principal should be on campus and have enough authority to deal with a reporter to that extent, at least.