In fairness you shouldn't of been warned for RDM, it is the bank vault and regardless of whether they are on duty or not they face a risk of dying in RP situations due to their inability to god/cloak.
From what you have said it seems you were unaware that there was a mod in the bank, thus you kept throwing the nitro.

By the sound of it he wasn't dealing with an F1 either, so again you had no idea that he was in the vault and so you continue to KOS anyone inside; just as any other player would.

Edit: He was in fact dealing with a "Prop Block" F1

In fairness you shouldn't of been warned for RDM, it is the bank vault and regardless of whether they are on duty or not they face a risk of dying in RP situations due to their inability to god/cloak. From what you have said it seems you were unaware that there was a mod in the bank, thus you kept throwing the nitro. [strike]By the sound of it he wasn't dealing with an F1 either, so again you had no idea that he was in the vault and so you continue to KOS anyone inside; just as any other player would.[/strike] Edit: He was in fact dealing with a "Prop Block" F1