Sgt Jackson is implied to be black and dies in the nuclear explosion at the end of the Marine arc.
SSgt. Griggs is the first member of the team to die in the final mission (although Gaz and many others soon follow)
(spoilers) ending is somewhat ambiguous, with much of the main cast getting killed/severely injured by the antagonist, before the player character is rescued
The US Marine arc of the story infamously ends with a nuke going off and killing your whole team, plus thousands of others.
The final string of missions has you infiltrate a missile base the bad guys have taken over to stop ICBMs from hitting the US and Europe, which you and your team succeed in doing.