Hughes and Armstrong in “Unfinished Business”

What I want to know is why this guy is only targeting State Alchemists and no one else? If it's the military he's trying to hurt, he could go after normal soldiers. Surely soldiers would be easier to kill than highly skilled alchemists, especially ones that have been State certified.

Maybe the certification is the reason. State Alchemists are given high pay and special privilege. It must be any number of people who envy them for their positions. Or perhaps, they feel they have not upheld their creed, Alchemists be thou for the people. Alchemists that were supposed to be pillars of science and truth are turned into the military's walking weapons as soon as they receive certification. There are plenty of people I'm sure who have not forgotten the role that State Alchemists played in the Ishvalan Civil War.