"We have listed both Tabun and Sarin. Be wary of the Doctor. His involvement should be minimized if
you want to make it out alive. We are unsure on how he arrived at this time and place. Do what
you must..."
Sarin is a nerve agent developed by the germans in the 1938. It interfers with the production and transmission of the enzyme cholinesterase, which normally allows muscles to relax after they have been contracted. Symptoms of sarin exposure are constriction of the pupils, as they are unable to relax, along with a runny nose, shortness of breath, and nausea. On one of the film rolls, it displays a pupil being normal and then dialated. Maybe this is demonstating the effect of sarin on a patient.
Tabun is also a nerve agent that effects the mammal nervous system. It is not as poisonous as sarin but it can be used to infect water supplys, not just the air. Tabun was developed in 1936 by the Germans. Upon contact, it causes similar symptoms to sarin but more irritation to the eyes. This was later used to make arial bombs when combined with chlorobenzene (a colorless flammable liquid)
These are both in the G-series of nerve agents along with soman and cyclosarin. They were both developed in germany in the 30's and were used in warfare along with mustard gas and cyclosarin. Possibly, in the beginning, group 935 was just supposed to develop weapons which moved onto super soldiers that turned to zombies. That is all I could get on it really.