Fun fact: This guys get a direct injection of something like dopamine when they enforce their authority, they make them feel pleasure when they mistreat civilians.

Civil Protection, or Metro Cops, are just normal people in suits without any biological modifications (think Barney when you first meet him while he's undercover), so Mike and Dave should be normal dudes under their suits. They would only turn into this if they moved up a level to become Combine Soldiers.