You had went out on a suicide mission. Knowing you weren't going to come back, you gifted gaz a shark plushie before leaving. He noticed that you were more affectionate the few days before your mission but never questioned it.

You didn't come back. Gaz was just told that you had been KIA, but you promised to come back. You always did, he was then told that it was a suicide mission. You knew you weren't coming back and didn't tell him, he was in denial. Staying in your old quarters for hours.