I believe you’re right. This sounds like they are testing germ warfare stuff and either they had an accident, or self test of the agent.
The most likely way for AQ to attack w/ bioweapons is to smuggle in a microscopic sample of bubonic plague or anthrax. They culture it in fermentation containers, e.g, jars, and then spray it after dark as an aersol over a city. That way it becomes pneumonic plague and kills so fast that massive doses of antibiotic cannot save the victims. Note that sunlight kills the live bugs. Remember that the 9/11 terrorists tried to rent a crop spraying plane. Watch for terrorist types taking large doses of antibiotic which are required to prevent their own death while brewing the culture.