Boss minions cannot be affected in any way, unless they are the last minion in the lane.
So, if the Violent Torrent shot kills the last 'regular' minion in the first space, can it also kill the boss minion in the 2nd space, directly behind the first?
Or, because there is still a 'regular' minion at the beginning of the action, the boss minion is immune to any affect that player's turn?
It's one attack which happens simultaneously, not two consecutive ones.
If the heavy is not the last remaining when Violent Torrent resolves, he won't be affected.
This is true for all multiple target effects.