I would have to assume, since we're dealing with what effectively become a homing, but uncontrolled projectile after proximity detonation, your case in point could be compared to a drifting mine set to automatically release munitions at the first ship that comes near it. After you fire the weapon, regardless of what target you had selected, the moment it submunitions it isn't following your target lock anymore, as it automatically seeks out the nearest ship under its own control.
In your situation, I'd have to say it's exactly as it looks and sounds like when read back to yourself, the weapon fires and homes toward the target you selected, collides with something in its path (an asteroid, or another ship), and then gives itself to free will, allowings its submunitions to fire at the nearest target, whatever that may be.
Essentially, a very non-judgemental homing missile. Good for space Russian Roulette, especially if you state that its submunitions can attack the player! :laugh: