As far as I know, the self defence is allowed even if there are admins online, so pretty much yes...
For the second one I think it depends and also it is up to you. If he is shooting to the air, you may tell him to stop and then suspect, or don't suspect, because he only wants you to do it.
If he is actually deathmatching, report to admins, of course. If he's shooting to you, that takes us again to Nº 1 answer.