Most doctors take an oath to do no harm, but that doesn't apply to the disgruntled corpsman. Getting wiped out by an invading orc army forces one to adapt lest they make the same mistake twice, so a few modifications were in order to keep battlefield physicians able to keep up with their fellows. You'll not find many true corpsmen anymore, none with the supposed marksmanship that blends into a cocktail of healing and desolation. Givers and takers of life, they're men of the bygone.
They call themselves CorpseMen now. Their practice is in death-strewn battlefields. You'll know when you find one.