"You have a no-fly one approved by the FAA for 48 hours," Oren Hale, Smith County's assistant fire marshal, tells a group of emergency responders.
"We didn't know the exact amount of cesium that was on board," another responder says.
"Well, they won't. But they can estimate the size of the cloud, the wind direction," one of the drill's trainers responds.
An explosion rocks South Tyler, releasing poisonous gas. In Whitehouse, a cloud of chlorine fills the air, after a train derailment ruptures a tanker car.
Mock disasters, but ones that could happen where you live, whether terrorists are to blame or merely human error.
Not only are local responders training for that possibility here. They know if disaster strikes in the Dallas, Fort Worth, or Houston areas, East Texas may have to step in and help.
"Some of our resources may be called on to go up there," Hale said. "We would have people being evacuated from the Dallas/Ft. Worth area coming to Tyler. We would have to handle those people."
"We can't be overrun with volunteers," another drill participant says.
The Red Cross and Salvation Army are practicing setting up shelters.
"I have 17 nurses, three doctors," an official with the Northeast Texas Public Health District says.
They're coordinating their efforts with local hospitals, like ETMC, which decontaminated mock patients yesterday.
The city of Tyler is also holding mock news conferences, so we, the media, can keep you informed in the event of disaster or terrorism.
"We have extensive collapse on both buildings," an emergency dispatcher says.
"There are always areas for improvements, but I think we have a real strong organization in place," David Schlottach, Tyler's assistant fire chief, said.
Tomorrow, the men and women in the first line of response will evaluate how well they would respond if today's scenarios ever really happened.