Nerve agents have been in the news recently; it seems likely that in England last week, an ex-Russian spy, Sergei Skripal, and his daughter were poisoned with one. The police officer that found them has also been hospitalized and now hundreds of people that may have come into contact with the toxin are being urged to launder their clothes.
British police have not yet specified which nerve agent was used on the victims, but the toxins tend to work in the same general way. Nerve cells use chemical signals to enable us to move, and one of those signals, acetylcholine, tells muscles to contract. An enzyme called acetylcholinesterase breaks that signal down, but nerve agents stop it from doing its job. That causes acetylcholine to build up and send a continuous contraction signal that can lead to spasms and breathing problems, among other adverse events.
The investigation would suggest that someone probably sprayed the agent on the victims where they were found, which would have also led to the medical emergency experienced by the responding police officer. Whoever recovers from this incident is likely to have lifelong health problems as a result, like headaches and fatigue.