Twatting someone out with a basketball, who was strapped and cutting loose on the kids, AFTER being hit himself?
I'm impressed. That guy deserves every bit of praise he gets. That took guts, and hell, to use a basketball to fuck the shooter up? that's creative, I like that kind of on the spot creativity. Hope the girl recovers.
As for terrorists...the problem is, IMO, that it'll always be a game weighted towards the terrorist faction du jour. WE have to get it right every time, we have to stop the terrorist or terrorists each and every single time, whilst they only have to pull it off once. As a numbers game, it favours the ragheads and other such filth heavily. We only need to have one slip the net, and there you go, a nailbomb in a shopping center, chemical weapons deployed, even bioweapons if someone is sophisticated and sly.
Chemical warfare agents aren't that difficult to make. Hell, I could, IF I wanted to, make sulfur mustard from sulfuric acid bog cleaner, bleach to act as a means to prepare chlorine gas with an oxidizer, or even electrolysis of salt, and using a calcium chloride drying tube to dry the chlorine, yes, table salt, then using agricultural sulfur, to prepare disulfur dichloride, and alcohol. Dehydration of alcohol, same synthesis I usually use to make ethers, but crank up the temperature, dehydrates ethyl alcohol to ethylene gas, this, passed through disulfur dichloride, which is prepared by chlorinating sulfur with elemental sulfur and elemental chlorine, and you have the agent commonly known as 'mustard gas', specifically sulfur mustard (there are two main classes, sulfur and nitrogen mustards), in this case, I mean (bis-2-chloroethyl)sulfide.
A Levinstein-style synthesis of sulfur mustard from things you can buy over the counter, and a bit of ingenuity.
Or one could use sulfur dichloride, SCl2, rather than S2Cl2, disulfur dichloride, and otherwise, the same, ethylene gas reacted with it, producing the crude mustard agent, if one decided to go with Depretz route, using SCl2. Either way, If I actually wanted to do it, I'd only need to buy the ethanol, vodka even, and dry it thoroughly, before using it to make the ethylene. If I had pure EtOH, it'd not take me long, and there isn't the slightest doubt, that I could do it with things I have right here, right now, with the one exception of ethanol. Could likely as not use isopropanol, which I do have.
I don't HAVE sulfur dichloride or disulfur dichloride, although they are damn useful, I'd just make the sulfur halide desired, or else use bromine rather than chlorine, as one problem I have found with making sulfur chlorides, is that molten sulfur is really quite viscous and thick, and it takes quite some pressure to drive the chlorine gas through the molten, liquid sulfur. No, the reason I've made such sulfur chlorides, is not making mustard 'gas' (it's a liquid, not a gas, but was dispersed as an aerosol in military use via explosive shells, or sprayed from aircraft), sulfur halides, as well as thionyl chloride (SOCl2) and sulfuryl chloride (sulfur oxychloride, SO2Cl2, one being a source of chlorine, the other of chloride IONS, in their reactions), are incredibly useful chemicals to have, for all manner of reactions. So are generally desirable to any hobby chemist, because of their versatility.
The crude initial product would have to be distilled, carefully of course, if it is to remain stable. This form being what the british codenamed 'HD' or 'pyro' in WWII, But I doubt a terrorist would give a fuck as long as they could use the crude product, and disperse it somewhere to cause mass casualties.
Not to say I myself, wish to make the stuff, I really don't want to be around blister agents, nasty shit, but COULD I make them if I wanted to? absolutely. And nothing special required, just stuff you can round up from garden centers, some bleach, some booze distilled to azeotropic concentration and then dried chemically, some concentrated sulfuric acid bog cleaner (which is usually between 98-99% although I have found 96% before. I don't use it if it can end up in a final product, such as making amphetamine sulfate, but for things like acid catalysis, dehydrating various things, making ethers, it works perfectly.) and you wouldn't even need the bleach and an oxidizer, if you decided to make a solution of table salt, subject it to electrolysis, dry the chlorine, or save effort and use liquid, easier to manipulate, in the context of halogenating sulfur, sulfur dibromide or disulfur dibromide would produce a bromine-substituted version of mustard gas, bis-2-(bromoethyl)sulfide, but in fact, due to the molecular method of action of sulfur mustards, the leaving group is important, and bromine is a better leaving group than chlorine, so it'd probably be even more effective.
Not going to try it, but a terrorist, all they need is ingenuity. It really isn't difficult.
Hell, nerve agents could be doable, or something like fluoroacetate, as fluoroacetyl fluoroacetate ester, which would be volatile, and very, very deadly, as fluoroacetate enters the Krebs cycle, gets metabolized like acetate would, to citrate, only in this case, to fluorocitrate, which jams up the works, by inhibiting the enzyme aconitase, and prevents cellular respiration, fucking up ATP production and starving cells of energy. It's near impossible to treat, a very, very unpleasant way to go, and lethal in small amounts.
Needn't even be a ciassic 'chemical weapon', there are plenty enough horrendously toxic easily generated compounds such a noxious little shit or group of shits could use to cause chaos and death. Hell, knock up a batch of one of the really potent fentanyl analogs, and that'd do it. Just look at the russian hostage crisis in that cinema, where they aerosolized a mixture of carfentanil and remifentanil in halothane (a fluorinated ether general anaesthetic of the volatile inhalation type, not used much now as it can release free fluoride ion after metabolism, which is harmful to the kidneys, superseded by more modern fluorinated ethers, such as sevoflurane, desflurane, enflurane etc.), pumped it into the building, it knocked out all the hostage takers, which were, AFAIK promptly given a bullet in the head while out cold by the spetznaz forces, but it also of course, KO'ed the hostages, and because the russkis were secretive about the agent used, many hostages died of an opioid OD.
Fuckers, they needn't have given their secret formula away, just said 'use naloxone' (an opioid antagonist, used to save victims of ODs, it'll bring someone round from not breathing, to conscious in moments after an IM injection, although anyone physically dependent on opioids that is treated thus after an OD, probably isn't going to thank you for saving them, that way at least, because it'll throw them into withdrawal, and not just any withdrawal, what they call 'precipitated withdrawal', many, many many times worse than the worst imaginable regular opioid WD. The sort of thing you'd set yourself on fire and jump out off the top of a multi-story building to make it stop kind of awful. I've never been subjected to it, I've never overdosed, I don't want to OD, but I'd like to be subjected to an opioid antagonist like that even less.
But the hostages, they could ALL have been saved, unless any had died before medics were on the scene. Naloxone, and bang, sorted. (might need multiple doses per individual as it's short acting, 10 minutes perhaps in some cases), and assuming they weren't opiate addicts, it'd probably not throw them into WD. No need to reveal the secret weapon, the same antidote is good for almost ALL opiates (save a few very uncommon types, with a higher binding affinity to opioid receptors than naloxone or naltrexone, meaning that these could not displace the opioid from the receptor once bound) Just tell them the drug type to use, 'opioid' isn't giving their secret technology away, but that knowledge would have saved the hostages.