Nichols was found guilty May 26 of 161 counts of first-degree murder for 160 victims and an unborn child in a state trial.
Nichols poisoned the water system in a small town
The context only mentioned that was guilty of murder, it never mentioned how he did it and therefore it is not known. 
( z0 poison :ARG0 ( z1 person :name ( z2 name :op "Nichols" ) ) :ARG1 ( z3 system :location ( z4 town :mod ( z5 small ) ) :mod ( z6 water ) ) )
(z0 / poison-01
    :ARG0 (z1 / person
              :name (z2 / name
                        :op1 "Nichols"))
    :ARG1 (z3 / system
              :location (z4 / town
                            :mod (z5 / small))
              :mod (z6 / water)))
Nichols poisoned the water system in a small town
z1 :name z2
z2 :op1 0
z0 :ARG0 z1
z3 :mod z6
z0 :ARG1 z3
z4 :mod z5
z3 :location z4