This will make no sense if you haven't played Ghosts. Also, since it's an alternate ending, there are spoilers.
The ending was disappointing to say the least, not ME3 disappointing but it wasn't good either. Honestly, it just seemed like a cheap sequel hook. I figured this would be a much more cohesive, if bittersweet, ending.
Apologies in advance for the generally low quality. I hacked this together in about twenty minutes.
"Logan! Do it!"
Adrenaline pumping through his veins, Logan aimed the revolved the best he could under the circumstances and pulled the trigger. Seemingly in slow motion, there was a bright flash and puff of smoke, the weapon pushed hard against his wrist. The bullet went exactly where he wanted it, straight through Rorke's heart. But it didn't stop there. It continued forward, tearing through Hesh's lung and tumbling out the back of his chest cavity, embedding itself in the already cracked windshield of the train. There was a brief look of horror on Rorke's face as he fell to the side, the Ghost falling with him.
There was a sickening gurgling cough, and Logan couldn't tell which of the men it was coming from. He limped quickly over to his brother, ignoring the ominous cracking of the glass just a few feet away. As he knelt down, David grabbed his arm.
"Finish the job," he sputtered quietly. His other trembling hand held a single cartridge. "Make sure he... doesn't get up."
Without hesitation, he took the offered round, loaded it, put the muzzle against Rorke's head and pulled the trigger. Blood, bone, and brain matter splatted all over the two Ghosts, the revolver, and the floor of the train.
"Good." That was all David managed to say before cracks spiderwebbed across the glass and water began flowing in, first at a trickle but rapidly increasing in flow. He managed, "Not good."
Logan knelt down beside his brother, who feebly tried to push him away as he propped him up against the side of the cab. "Go. Leave me. Get out of here."
"We're a hundred feet down, the train's collapsed, and I've got a bullet in my leg." The water was up to his ankles now. "This is the end, brother. Neither of us are getting out of here."
After a long, ponderous moment, which felt like hours but couldn't have been more than a few seconds, David quietly asked, "Which way is home?"
That one took a few seconds, long enough for the water to make it up to his shins. "To the north, so that way." He pointed.
"Can't lay down... I guess this'll have to do," David mumbled, gritting his teeth against the pain as he manoeuvred himself to face in the direction his brother pointed out.
Logan set himself down behind him, picking up his brother's dropped rifle and setting it next to him. "It'll have to."
"We did Dad proud," David stated, his voice barely a whisper.
"Yeah, we did." Logan replied. There was no response. His brother had passed out from the blood loss.
"See you on the other side," Logan whispered as the glass finally gave way and a torrent of water enveloped him.