Former theatre manager here: yes, it's because it was hot. When we had a heat wave in San Diego, where nobody has A/C, we would get sold out shows, lines all the way down the block, and it would roll over: if the show someone wanted was sold out, they would see the next thing. Didn't matter what. And inevitably, one of the houses' A/C would fail. Usually the largest one, because it was working the hardest, and because the hall and lobby didn't have A/C. Then sometimes it would start flooding the booth, and dripping into the back of the theatre.
Anyway, when Gus mentioned the shooter and Andrew said "Jesus Christ!" my captioning just said "Chris!" So according to the captions, you have to watch out for that guy. I can't see it, so it was funny.