So, I was doing AK with some friends today, though the tank was new.
He pulled the Priest towards the entrance of the boss zone and about 1/4 to maybe 1/2 of the Priest's life bar, he went nuts! And ran out of the room.

The SMN and myself /return to see if we could kill it. Who doesn't want to know if it's possible to kill the Priest before he summons the Squid boss? Well, we found out... It's not possible!

Here's some SS! Please fix or find out why / how this happened