One may pre-empt an action that one can see.... one can pre-empt someone pulling a gun, but not using telepathy (Auspex 4). You, in turn, may be pre-empted by someone with this power. The person with the higher celerity goes first. If equal, whomever pre-empted last goes first.
You may take Two actions in a round instead of one.
You may take Three actions in a round instead of one.
You may take Four actions in a round instead of one.
You may take Five actions in a round instead of one.