Maybe they were purposely vague about his death in case they want to bring him back. They did that on 24 with Shoreh Ashdagloo, but they ended up not bringing her back. Perhaps they did that with Rex, too. The door is open if they decide to bring him back at some point, but they can leave him dead and it still makes sense.

"You know, I have this weird feeling that growing up is overrated."
2nd season on DVD August 23rd!!