To the OP:
Think this. Imagine that tomorrow, in middle of this pandemic, future elections, and things like that Chicago is all but destroyed. You are not there. But perhaps you or something you know have family there. And that family survived and tells you all what happened. A big Titan, monsters in the streets. At the same time you read in newspapers, social networks (Supernatural people uses social networks too, except for the wizards), TV, radio tells you that there was a terrorist attack, and some massive allucinations around, probably because of gases or drugs or whatever.
Who would you believe? Wouldn't you think that perhaps the Chicagoan were traumatized for so much slaughter, pain, destruction?
I have an example more on point that WW2 or the nuclear bombs, which were natural. Do you believe the Fatima miracles actually happened? Only around 100 years ago, not 600 or anything, in a time were some cameras already existed and some skepticism were around, literally hundreds of people claim to have seen the Virgin Mary. And more than once. Yes, there are not 8 million people, but there are quite a bunch. And do you, personally, believe it? Probably not, because they told you that they are lying or they had been victims of massive hysteria. Why wouldn't the same logic apply to Chicago?
That said, it's obvious that not everyone will believe the official story. But if denial happens even about tragic real natural things why wouldn't it happen for supernatural things, and much more. We all want to sleep better at night.
Still, I wouldn't go with terrorism. I would have gone, as suggested, with a hurricane or something. And then I would have said that gangs terrorized people who where in such a state of desperation, panic and pain that they thought they were monsters.