He keeps it together, more or less, through the whole case. He's had a lot of practice, shoving it down, shoving it away, so that's what he does. He boxes up the pain and the fear and the grief and sticks it on a shelf and if it rattles or threatens to spill open, well at least it stays on that shelf.
When Al walked into the viewing room the words were a sledgehammer to the chest – "Terry, he, uh, didn't make it. Massive hemorrhaging" - and he stopped seeing Brianna, Erin, and Voight on the other side of the glass. All he could see was the blood on Terry's lips as he begged, "not like this, brother," and it bubbling through up through Jay's own fingers, hold on brother, just hold on, and when Al kept talking it was like it was coming through the end of a long tunnel, and he was teetering on some kind of edge – not like this – and the small dim room was stifling with Al standing next to him, he had to get out, had to breathe, put it in a box, put it in a box, keep it together, so he brushed out of the room, clenched his hands in fists, nails digging into his palms – deep breaths – and packed it away in that box.
When he walks into Terry's house – not like this, brother – he walks into a force field just outside the room, a force field made of Lissa's smiling face and the grainy black and white ultrasound and Terry's arm around her shoulder, and he imagines her now and he stalls out, a broken down car in the hallway because this is too familiar, there's a wife in that room whose husband died while Jay survived and he can't breathe again, but he owes her this. He's not allowed to run from this, he can't, she deserves better, he owes her, and he owes Terry so he braces himself – deep breaths – and walks in and it's as bad as he thought it would be, maybe worse because there she is, looking at him with soft sympathy, like she's sorry for him, like she wants to make sure he's okay, she says his name softly, gently. But he owes her strength, he owes her this, so he keeps it together.
Standing in front of Briggs makes him feel sick, and he's talking around the lump threatening in his throat and he wants to rip open that cage and tear him apart, make him pay, blood for blood, and then Voight is opening the cage – "you've got five minutes" – and he's handing over his gun curling his fists, yanking open the door, because he's got to keep it together, keep everything in that box but this, this feels a lot like setting that box on fire and he wants to shove the flames down Briggs' throat and he thinks maybe he can handle the box when all that's left are ashes, until Antonio calls out and it's a whole new sledgehammer and it takes a minute to regain his footing but he does because – keep it together – he's gonna get the son of a bitch who pulled the trigger.
And he does. And he's standing over him, foot on his throat, pressing just enough, and he thinks for a second – Voight would understand – because the box is rattling. But then there's a flashlight, and Al behind it, and he pulls his foot away, because he's not Voight, because there was a reason he went to the docks that night way back then, there was a reason, and he won't forget that, he can't, so he lets Terry's murderer get packed up into an ambo and shipped off.
He hasn't worn his uniform in a while – not long enough, never long enough – and he looks in the mirror only long enough to make sure everything is in place, no longer. Erin sits beside him but he's barely conscious of her at all, staring at the picture of Terry – he looks so young, so young, he was so young – letting the Father's words wash over him – just breathe, breathe, keep it together – sitting stiff and upright until the funeral is over, and he takes the uniform off as soon as he can, folds it up and packs it away where he keeps it out of sight because despite the crisp clean fabric, the smell of death clings to it.
He kept it together, more or less, through the whole case. And he knows, god does he know, that sometimes the oddest things can set people off. But of all the places for the linchpin to be, all the people to pull it, he wasn't expecting it to be Voight.
"I'm lucky to have you in my unit."
Jay had already been turning away, ready to head home, ready to sleep, figure out what the hell he was going to do with this week of medical leave when Voight called him back, tossing out these words like they simple. Like they were easy, provable truth. Linchpin.
He makes it to the locker room – breathe, just breathe – gripping the edges of the sink – breathe, pull it together – flicking on the tap, the cold water, sticking his hand under to… to do something, but he gets lost hallway, pulls his hand back, flicks the tap off – just breathe – not sure what he's doing, what to do with his hands, where to look, he glances up, catching his own gaze in the mirror – not like this brother, not like this – and the cut on his cheek, red and raw reminds him of the blood on Terry's lips, reminds him of Terry's blood on his own face, Terry, bleeding out on the pavement in front of him, Terry dying, dying, dying, and Jay could do nothing – I'm lucky to have you in my unit – and he can't look at himself in the mirror, and he's trying to keep the box closed, but it's crashing to the floor, spilling open, Jay is falling to the floor, breaking open against the cold tile – not like this just hold on massive hemorrhage he really looked up to you think you can manage that pretty boy lucky to have you in my unit my fault my fault my fault lucky my fault not like this brother.
It's a long time before he can stop the tears, stop shaking, start breathing again. His whole body aches, stiff and hollow and bone deep, and he gathers his things and goes home alone in the cold and the dark.