Combat Medics

Chapter IV, Article 25 the Geneva Convention states that "Members the armed forces specially trained for employment, should the need arise, as hospital orderlies, nurses or auxiliary stretcher-bearers, in the search for or the collection, transport or treatment the wounded and sick shall likewise be respected and protected if they are carrying out these duties at the time when they come into contact with the enemy or fall into his hands." Article 29 reads "Members the personnel designated in Article 25 who have fallen into the hands the enemy, shall be prisoners war, but shall be employed on their medical duties insar as the need arises."
According to the Geneva Convention, knowingly firing at a medic wearing clear insignia is a war crime.
In modern times, most combat medics carry a personal weapon, to be used to protect themselves and the wounded or sick in their care. When and if they use their arms fensively, or carry arms that qualify as fensive, they then sacrifice their protection under the Geneva Conventions.