When religions get involved in terrorism, it is never just a religion, it is a political group with political aims, under the guise of religious zealotry.
If you want to charge everybody engaged in hooligannery with terrorism, be my guest - but it is a waste of time when the terrorists we want are the prolific ones who do it all the time for political, psuedo-religious reasons. I don't want to dilute our anti-terror resources and credentials to go after an idiot who let a poisonous snake loose in a theater. Yes, local police should get on it and find the perpetrator and throw the book at him, but getting the NSA, FBI, and CIA involved would be overkill without evidence that it is part of a concerted effort to kill large numbers of Americans or create fear of public spaces in large numbers.
> getting the NSA, FBI, and CIA involved would be overkill
Who says you need to?