Does %obj.killBrick(); even work?
That destroys bricks as if they've been hit with the Admin Wand, permanently...
I think %obj.fakeKill(time) is only in v9.
If you want them to be killed rather than "exploded" like minigames then you should use a radius search in the onCollision for $TypeMasks::FXBrickObjectType using %obj.killBrick(). If you want temporary damage, just use the built in brick damage functions:
datablock ProjectileData(rocketLauncherProjectile)
{
...
brickExplosionRadius = 3;
brickExplosionImpact = false; //destroy a brick if we hit it directly?
brickExplosionForce = 30;
brickExplosionMaxVolume = 30; //max volume of bricks that we can destroy
brickExplosionMaxVolumeFloating = 60; //max volume of bricks that we can destroy if they aren't connected to the ground (should always be >= brickExplosionMaxVolume)
...
};