Quest mount/pet abuser

Hello Warmaners :)

Today some Troll Hunter named Jentrazwaz killed my girlfriend, so i decided to return the favour.
All of a sudden we both got 2shot by something that looked like a weird Explosive Trap.
Apparently some player named Halbrecht, a Tauren Warrior, used this mount/pet to kill us multiple times.
It is a Wyrmrest Vanquisher, I have multiple screenshots.
It does about 15-16k damage per blast thingemy, Englufing Fireball.
The mount probably flies slowly, because after Sholazar Basin, I saw the hunter in Storm Peaks where he followed me around for a while after I killed him again.
After the long follow, we started getting 1-2shot again.
It also seems to shoot through the cave partially
I also saw Halbrecht on the ground and Jentrazwaz on the Wyrmrest Vanquisher.

Is what these players did okay? Is this bannable?
I doubt this pet/mount was made to kill people.

The Imgur album: http://imgur.com/a/mfvCe