[FT] Kra'Vak Scattergun question

FB2, page 10, para. 6 talks about using Scatterguns in the 
area-defense role. 
    "...if the effect roll scores a ONE then some of the
     scattergun projectiles hit the ship that is being defended,..."

Does this mean that friendly fire occurs when a "1" is rolled or
when 1 fighter/missile etc. is destroyed.

For example, if the attacking fighters are heavy, then the number of
hits is half of 1D6 rounded up.  Since rolling a 1 or a 2 results in
one fighter kill, do both of these result in friendly fire?

If the fighters were not heavy, then only rolling a 1 will cause
friendly fire.

--Greg