This oneshot happens before the continuity of "A Paper Wall"; it's most directly related to the flashbacks that open chapters 7 and 15 (the ones about Splinter's hide-and-seek game). It also stands on its own pretty well, and doesn't spoil anything from the main story.
The First Time
The first time one of them actually gets shot, they are still fifteen.
A click, a bang, a choking cry, and a heavy thump.
It's still echoing in his mind.
Leo sits for hours, watching his own blood leak slowly into his brother's arm, wishing that he could likewise slide a sense of self-preservation drop by drop into Raphael's veins.
It's a long night.
When Raph wakes up, his words are mangled, and Leo is terrified that the bullet has poisoned him, has damaged his brain. But a little while later Raph is speaking as clearly as he ever does, wanting to know whether everyone else is okay, wanting to know what they did to the moron with the gun.
"We got him," Leo says. "Mike got him."
He had never seen Mike go after anyone with that degree of hatred. His youngest brother had come back with a grim look on his face and a new brokenness in his soul. "Let's go," Mike had said, and they did.
Leo had known, then, that Mike had killed someone. But Mike had disappeared as soon as they got home, giving Leo no chance to talk to him about it. And so Leo focused on the brother whose wounds were on the outside, the one he could fix with bandages and thread and offerings of blood.
Raph spends a few days in the infirmary. Don orders him to stay there, even when Raph insists he's fine. When Don finally allows him up, it's obvious that Raph is not fine. He walks with a pronounced limp, the wound in his leg slowing him down and causing him pain. Leo fears that the damage is permanent.
But, as the weeks go by, Raph's muscle repairs itself, and his strength returns. Before long he's back to his old self, with only a puckered scar on his thigh to remind them of that terrible night.
It's enough of a reminder for Leo. Now that there's nothing more he can do for Raph, his attention turns towards Mike, and the invisible scars he carries from that night. He tries, repeatedly, to talk to Mike about it, to heal him with words and with empathy, but all his efforts are ignored, rejected, with a cold silence.
Eventually, he stops trying. There's always another problem, another thing to fix, and he can't keep burning up his energy where it isn't doing any good. He leaves Mike alone, to nurse his hurt in quiet corners.
But he doesn't forget.
The subject of what Mike had done that night isn't brought up again until months later, when the ice is finally broken by Donnie's first kill. Donatello is the last of the brothers to take a life, and not the one least disturbed by it.
After the battle, Leo stands to the side while Raph holds their stunned brother. The first to give death, the one who has come closest to receiving it, he tries to lend comfort and strength, to soothe the pain of this unwanted rite of passage. "Let's go," Leo says, and they do.
At home, Leo cleans Don's wounds, because Don can't seem to do it himself. He just stares at them, runs his hands across them, smears the welling blood into his palms.
"Stop," Leo says softly, catching Don's wrists. Don only looks at him with hollow eyes, and shivers.
A few hours later, they're sitting in the living room, each absorbed in his own thoughts.
"I felt him go," Don says, into the quiet. "Just -" He turns his hand sharply. "There. Not there."
"Mine was slow," Mike says, and they all look at him, surprised at his sudden candidness. "And I said to him... You only get one shot. You shouldn't've wasted it."
Don covers his face.
"Damn shame," Raph says. "Their own damn fault for comin' around pickin' fights with us. They could be doin' somethin' so much better."
"We're no better than them," Don says brokenly. "We're no different."
"No," Leo says. "They fight to kill. We fight to live. That makes all the difference." He puts his arm around Donatello, pulls him to his shoulder, wills him to believe that the distinction is more than a trick of words.
Splinter comes in with a tray of candles, sets them on the low table, and turns off the lamp, the only light they'd been using.
They consider the flames.
Two of the candles have clearly been lit, and then extinguished, their wicks blackened and their wax runny. The other two are still burning.
Leo feels a tightness in his chest. He remembers, little more than a year ago, Raphael blowing out a candle and being engulfed in darkness. A few months after that, he had blown out his own candle. Now, Michelangelo and Donatello face the same symbolic transition.
Like a well-forged sword, his connection to his brothers is folded again, made stronger in the inferno.
In this hell where their lives depend on their willingness to cut off someone else's.
They sit in the flickering circle of light.
Michelangelo leans forward and blows out his candle. After months of silence, he accepts his choice. A slow breath, and the light goes out, the smoke curling upwards.
They turn to Donnie, but he doesn't move.
He doesn't move for an hour.
Then, as they're all watching the little flame sputter in its puddle of wax, he leans forward and gently blows it out.
In the dark, they understand. Darkness comes, always. But they don't hasten its coming. They only, at the last moment, choose how it will come.
Whether it will cover their eyes with a veil that never lifts, or whether it will leave a black smudge over their hearts. Whether it will come painfully, choking and gurgling and fighting, or swiftly, mercifully, there, and then not.
Don has shown them the difference, more eloquently than Leo ever could have said it.
And they are together, in the dark, in this brotherhood of blood.
And, in a little while, they'll turn the lamp on. They'll live in the light, and they'll pretend they don't know that the darkness is always hiding just behind it.