Multiple Combat question

Here's some questions that came up in a recent game.

Scenario is Tyranids vs Space Marines.

Turn 4, Tyranids have 3 10 man unit of gaunts in combat with a space marine Captain in Terminator armour. Let's call them unit A, B, and C.

They each have one model in base contact and the rest are surrounding the Termi.

This has been an ongoing combat since turn 3.

So the space marines send a tactical squad now that it's bottom of turn 4. To assault 1 of the units in the combat. However they take a difficult terrain test to assault said unit getting a 4 and barely reach 2 Gaunts in Tyranid unit C.

The gaunts from unit C all get wiped out by the marines and the Terminator Captain also gets killed by the Gaunts in unit A & B in return.

So now units A n B are not in base contact with any enemy models (they were only in contact with the captain) and the tactical squad wiped out unit C which it assaulted and which was previously engaged with the Captain.

So does everyone consolidate or does the tactical squad get to keep all the gaunts from units A and B stuck in combat through "Pile-In" moves even though it had no models in base with it and did not allocate any attacks or anything onto them as they were only engaged with the captain.

I know that because they attacked unit C which was engaged with same captain that units A & B were engaged with, that the whole thing becomes a multiple-combat for determining which side lost and taking no retreat saves and all that.


My second question is pretty straight forward.

Can you shoot THROUGH combat? Is there a rule that prevents shooting through combat in the way it did in 4th edition?