For your first question, No. You arent to shoot medics at all, unless in a red zone and you want to get an easy frag XD. If the medic hears the shots they HAVE to leave, (9.2.4) Combat Reviving - If combat is in effect, or shots have been fired within the last 5 minutes, the area is not safe to enter for rescuing the injured. Therefore, you cannot revive at this time. This rule is exempt for civilians using defibrillators. If they fail to leave and proceed to land this initially is a break of server and NHS rules. Don't shoot them as 2 wrongs don't make a right. If they land you can refuse them access to the downed person, they should try to barter with you and negotiate the treatment but your words are final, once again if they fail to acknowledge this is a break of Server and NHS Rules.
If a medic is killed in a crossfire, yes it happens, Firstly try to prevent starting gunfights whilst a medic is Roleplaying otherwise you ruin there RP and pisses them off! If they are killed and you can prove it was unintentional that's fine but the evidence must be sufficient also you have the fact that yes, you cant see skins but medics are unarmed so shouldn't be a target in the first place.
Hope that answers your questions, if not let me know,
- DR Louie Austino