I thought his voice at the end was him reflecting on the humans kicking his butt during their war 100,000 years prior. I don't recall the exact wording, but I assumed this was that or perhaps the weird "second form" thing the Forerunners take on when they die (Bornstellar talks about this in the beginning of Cryptum).
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[quote][b]Posted by:[/b] terroboy He'd dead that grenade didn't kill him but that fall most definitely did. [/quote] Forerunner armour is very good at keeping it's user alive. The fall wouldn't kill him. He's immune to the Composer so he would have just fallen into the slipspace portal and been sent to wherever he was sending the composed humans.