John had told him not to go ahead.
Or, if he hadn't, it had surely been implied in the way that he hissed Sherlock's name as the detective took off running up the stairs. But, like usual, Sherlock hadn't listened, John was left swearing at his ex-flatmate's incompetance, and left with the itch to take off running after him, because that was what they did.
He didn't, though, because Janine was a friend, and nevermind Sherlock's insistance on using people for a means to an end, John was pretty sure that Sherlock cared about Janine on some - maybe a very small, pushed away one - level.
All of that no longer mattered when he heard the gunshot.
John took the stairs two at a time. "Sherlock?"
He had told him not to go ahead.
He had told him not to go alone.
"Sherlock?" John rounded into the room, pausing momentarily because, was that Magnussen? He'd been here, all along, and then: "Sherlock!"
The detective wasn't moving. Was he breathing?
For one, long instant, John was two and a half years prior, standing outside of St Bartholomew's hospital, rain dancing against his face, lifeless skin beneath his hands, "let me through, he's my friend, please", blood on the pavement and oxygen too thick and heavy to get into his own lungs as his legs buckled and "oh, God, no".
He shook himself hard and crashed down next to Sherlock's body, feeling first for a pulse out of instinct, and then going to the wound, ripping Sherlock's jacket open to apply pressure to the wound. Through all of this, he was aware that he was talking, although he didn't hang onto the words: "Sherlock? Sherlock, wake up. Open your eyes, you bastard, you are not faking out on me this time. Sherlock. Come on, you have to stay with me. Sherlock!"
Ambulance. Think. Keeping a one-handed pressure on Sherlock's chest, he jerked his own phone from his pocket, dialling 999. "Ambulance," he snapped, and his voice did not waver, it did not, and he glared towards Magnussen, who was just now moving. (Why him, why was Magnussen the one moving, not Sherlock? What the fuck had happened?) "What happened?" he demanded, masking fear with anger, the obvious answer coming when Magnussen replied