There's an interesting safety advisory addressed to the Canadian Forces that's recently been posted on the TSB website. At the time of the accident, Canadian Forces had set up a temporary Class D control zone at YRB to support a military operation, but did not have the capability to maintain radar-based or non-radar IFR separation. There was a loss of separation between the First Air flight and another aircraft which, according to the advisory, could have resulted in a mid-air collision "had the First Air flight not hit the ground".
Presumably, along with whatever else they were dealing with, the First Air crew had a TCAS alert at low altitude in landing config. There's no information in the advisory on the other aircraft involved (are military aircraft Mode S/TCAS equipped?).