The Bulgarian Secret Police with the help of the KGB once killed a guy by the name of Georgi Markov on the streets of London using an umbrela with ricin in the tip. The assassin pricked the back of Mr. Markov's leg and administered enough ricin to kill him.
You guys are right - that is some nasty $hit. My old labmates at UT were doing some studies on it; finding chemical information such as its molecular structure, and experimenting with inhibitors. Now, if only somebody on the pharmaceutical end could get that into drug form (non-toxic to the rest of the system and able to be delivered to the appropriate target). Unfortunately, our group's work was just the beginning. To make a long story short, ricin is a protein that occurs in grains and certain plants in very small amounts. Isolated and concentrated, it becomes a potent toxin. When the molecule enters your cells and breaks into its two components, it is very efficient at stopping the protein synthesis process that drives the life of your cells. This could take care of you very, very fast. The researchers refer to ricin and other "Ribosome Inactivating Proteins" as "RIPs". I know that just comes from the initials, but it's kind of appropriate that it's also something that would be put on your tombstone. Definitely a nasty possibility for biological warfare.
I just hope those six men had all of ricin, because this may have devestating effects if used as a bioweapon.