Nota bene that Tom Clancy had his villain crash a plane into the US Capitol a decade before 9/11 happened. With that prologue, consider the following notional scenario:
As people streamed into the Staples Center for the night’s game, the sun was just going down on a beautiful early spring day in Southern California. At separate entrances, and separated by several minutes between arrivals, 12 elderly Middle Eastern senior citizens were wheeled inside by doting younger relatives. Grandfathers and grandsons, uncles and nephews. Each one sat in a standard folding wheelchair. Behind each elderly man were 12 identical “C” size oxygen canisters. Each passenger helpfully had a nasal cannula hooked beneath their nose, but a carefully placed blanket or jacket in each case concealed the fact that they weren’t connected to the cylinder outlets, just dummied in place. One by one, they found their seats at the railing of the upper level, spread around to each number of the clock, beside an aisle. The wheelchairs were left behind the back row, folded up, but the O2 bottles were carefully carried alongside each elder until the pairs had found the seats and settled in. They say down and waited. They stood for the national anthem, and let the game start. Precisely 5 minutes into the first period, each pair got up. To get a hot dog, visit the bathroom, whatever. As they stepped away, each young attendant, having checked to see the spray outlet was pointed at the center of the arena over the railing, quickly but nonchalantly twisted open the valves, and then hopped a quick couple of steps, calling after their elder charges, and headed to the upper landing. Whereupon a miraculous change in spryness enabled each pair to calmly but quickly exit the arena, again by different exits, and were picked up in each case by a third accomplice who brought the cars near the curb. Within a couple of minutes, they were all heading outbound towards one of the nearby multiple freeways, and back to their safe houses. Back in the arena, a dozen cylinders all poured out an invisible vapor of aerosol droplets. The twelve tanks had been smuggled north from Mexico, after being delivered from a freighter off the coast, and run into a shore rendezvous off Baja, then smuggled along drug routes through the border deserts before winding up at the group’s warehouse near downtown L.A. Each was painted to resemble an oxygen tank of medical O2, but all in fact held under pressure a particularly well-made batch of Sarin liquid nerve agent. Air currents inside the venue distributed it widely, and within minutes, people on the lower level began to feel “wrong”. Their vision was constricted by closing pupils and teary eyes, they were coughing, then noses ran, then they began to gag and gasp and vomit. Their nerves spasmed, they stumbled, and as they all began to slump to the ground, lost control of their bladders and bowels as they landed heavily on the floors and aisles. As others noticed that something must be going on, they tried to flee, but the vapor cloud found most. Especially bad was the fact that everyone inside the ring of death had to pass under the cascading aerosol of droplets from above. Pretty much everyone on the lower level was minutes from death the moment the cylinders were cracked. The people on the upper level had things somewhat better, having only gotten a mild dosing from what the air circulation system distributed. But what nerve gas didn’t kill, panic did. Dozens were trampled in the melee for the exits. Some who’d received gas in their eyes, noses, and mouths began to go down in ones and twos, in a trail leading from the seats to their cars. Others who had a few more minutes from skin exposure lost it trying to get to their cars, strewing bodies all over the parking lots. Some smaller number succumbed on nearby streets and freeways, creating the mother of all traffic jams in every direction, and every accident a contaminated hazmat response.
And all the while the carnage was broadcast live on TV to millions of viewers, some by stunned cameramen, some by cameras whose operators were already dying under the lenses. In the confusion and panic, it was over 3 minutes before someone in the truck yanked the signal feed circuit. One of the vehicles was simply driven away with no attempt to disconnect, and toppled a dozen fleeing bystanders before the cable snapped on a fenceline.
At Los Angeles MFC, dispatch started getting panicky radio calls, and several fire and police units were dispatched. Long before they arrived at the "Major Emergency - Hazmat", they were called off, and a perimeter was called for upwind. The Hazmat Response crews were dispatched. By the time they arrived twenty minutes later, and took another ten minutes to get suited up properly, it was a body hunt and forensic investigation. Inside over 10,000 people were dead. Another 1000 bodies were scattered throughout the facility, and there were over 200 nearby traffic accidents. An unfortunate number of the first arriving paramedics and patrol officers became secondary casualties in short order, leading to futile attempts to establishing several hundred secondary contamination zones, and evacuating thousands of residents nearby and downwind. Between 24 hour news and sports radio, and cell phones, panic spread at the speed of electrons.The populace collectively lost their minds. To both nearby residents and those listening and watching the game, it quickly became obvious that somebody had used something. People started grabbing car keys, and maybe whatever they could grab in 30 seconds, and hit the road en masse. A cascading traffic snarl spread outward from south of downtown, near the original incident. As word spread from city radios to commercial broadcast about the secondary sites at accidents nearby, getting in a fender bender, instead of getting out to exchange info, became a game with rules somewhere between a demolition derby and Death Race 2000. And as the cars fled the locus of disaster, outlying cities and surrounding counties fumbled and wondered what response to take. No one had ever tried to deal with 5 million cars all headed out of L.A. at the same time, driven by people ranging from cautiously determined to ragingly hysterical.
Between the incredible number of traffic accidents, including the contaminated victims, and the number of slightly contaminated or uncontaminated but terrified spectators and their families arriving in the local ERs, hospital after hospital was flooded with patients. Operating on the ragged edge of disaster on a good day, the entire county’s emergency medical system had a stroke. Ambulances nearby were contaminated, some crews dead, others couldn’t get to calls, let alone the normal nights’ tally of gunshot victims and heart attacks. Diversion of ambulances to and from farther and farther away spread like ripples in a pond, and within an hour crashed the entire system. Which in turn impacted the systems in surrounding Ventura, Orange, San Bernardino, and Riverside counties. By 10PM, nearly 10% of the population of the United States – 30 million people - centered on Los Angeles was effectively left without any emergency medical service until further notice.Not that there were more than a 100-200 doses of atropine in all the local hospitals combined, and it would be hours before anyone could access federal stocks of nerve agent antidote. By which point, everyone who’d need it would probably be cold and dead anyway.