I blame the gunman. You can blame the theater chain but that’s just goofy.
It’s no more goofy than if they chained the fire exits closed and someone set fire to the theater. They created a safe killing zone in their theater.
They asked for demanded it, they got it.
As folks say here in Texas, "You're plumb eat up with the dumb@$$!"
With their anti-gun rules, criminal accomplice, Cinemark, guaranteed that the gunman (primary culprit -- I agree) could proceed unopposed until he ran out of ammo or got tired -- whichever came first.
Granted, the madman was armored and helmeted. However, the shock of a round striking a helmet is a BIG, disorienting distraction. And civilian body armor transmits sufficient force to cause intense pain and injury. (Google "backface trauma" and "backface signature injury" for verification.)
Even with nothing more than a 9mm, a competent shooter could have drastically shortened that madman's murderous rampage. But that option was denied by the criminal Cinemark policy...
Cinemark and its "no guns" policy simply concentrated the law-abiding as a mass victim target -- and did nothing to impede the lawless monster from wreaking havoc.