The cabbie is dying, that much is clear. The shoulder wound might have been survivable in theory, especially since the bullet passed cleanly through, but the blood is being lost too quickly and of course there is no medical attention in sight. Sherlock estimates he has less than thirty seconds before the man loses consciousness, not nearly long enough for all of the questions he still needs answers to. He has to settle for the most pressing one.
“Okay, tell me this: your sponsor, who was it? The one who told you about me—my fan. I want a name.”
“You're dying and there's still time to hurt you,” Sherlock points out, then places his foot on the bullet wound and grinds it. “Give me a name. A name! Now! The NAME!” The man...the serial killer... is dying horribly anyway, surely it doesn’t matter if his last few seconds are slightly more painful than they might otherwise have been? In the back of his head he hears a voice say “a bit not good” but he ignores it. Clearly the time for any sort of moral qualms passed when he got into the back of a cab driven by a murderer.
“John!” the cabbie finally cries with what appears to have been his literal last breath, as he expires seconds after.
Sherlock is still puzzling over the name half an hour later, which is why it takes him so long to notice the strange orange blanket draped over his shoulders. John... should be male, obviously, though after his earlier mistake with “Harry” he probably shouldn’t eliminate females just yet. It’s consistently in the top ten most common male names in the UK, there are millions of Johns, he’s probably talked to.... three today alone. Three point five if you count middle names. If you count language variants the count rises to seven. It’s a name, but not much of one.
Lestrade interrupts his thoughts to ask about the mysterious shooter. Boring. The killer’s sponsor is much more interesting. But maybe if they catch the shooter it will bring them closer to John? Or at least go away and take their idiotic blankets with them?
He sighs and explains, “The bullet they just dug out of the wall is from a handgun. A kill shot over that distance, from that kind of a weapon, that's a crack shot you're looking for but not just a marksman, a fighter. His hands couldn't have shaken at all so clearly he's acclimatized to violence. He didn't fire until I was in immediate danger though so strong moral principle. You're looking for a man probably with a history of military service and... nerves of steel—” And at that moment, he suddenly notices Dr. John H. Watson, standing at the periphery of the cordoned off area in a bland looking jumper and a ‘nothing to see here’ expression. “Actually, do you know what, ignore me.”
“Sorry?” Lestrade asks, stunned less by the flow of information than by its abrupt cessation.
“Ignore all of that. It's just the, ah, the shock talking.”
He already had a feeling he and his new roommate were going to get on famously.