Sometime after they've taken him away, but before they bring out the hose to wash away his blood, John goes home.
The first thing he does when he returns to the flat is take his phone from his trousers pocket (won't be needing this now), wrap his cold fingers around its body-warmed steel, and hurl the bloody thing at the wall. He wants it to shatter into shrapnel, and maybe he even wants to be caught in the crossfire, but the phone simply hits the spidery brocade with a dull thud and falls heavily to the floor.
And there it lies, and John stares at it unmoving.
There's a narrative of the day beginning to take shape in the back of his mind, entirely against his will, and it occurs to him that the flat is too quiet - too still - except for a distant ache that echoes... in his head, maybe. He can't quite tell.
John pinches the bridge of his nose and rubs dry eyes, and the pain settles in lower, dropping down into his throat to tighten around a swallow he cannot make.
And then he's choking, sinking to all fours as the room spins, and it's all he can do to prop himself up as he heaves in great gasps. A dull tingling sensation in his extremities tells him that he's hyperventilating, and some clinical part of him thinks that's a good thing to know.
John doesn't notice when the hoarse pants bursting from his lungs turn to a guttural wail, clawing its way up his esophagus and out into the air. It has no form, no melody; it's not the soft cry of the bereaved, but a howl (ah god) ripped from his chest and bleeding down the walls, staining them with his despair.
After (a minute an hour a day), John hears a distant thunder. The door flies open, and it's not Mrs. Hudson, wringing her hands in the doorway, who crosses to John's side, but Lestrade, bending down on one knee and grasping his shoulders to meet his glassy gaze.
And there's no need for words. Sherlock will forever be falling in John's eyes, plain for the world to see.