DroopyB

Just finished watching episode on Netfilx, and it is pretty simple actually. Earlier in the scene, when he looks down, you see a homeless person with a large bag at a bench at the base of the building. He ensures John stays in a specific spot when he is talking to him, even asking him to back up at one point. He coordinates with Molly earlier in the episode, she works in the morgue. The homeless person sets up an air bag for him to fall on. It is then deflated and removed (which is why John gets knocked over by bicycle). Sherlock places himself on pavement with some blood. Perhaps some medications to slow his reperation and heart rate. Molly revives him in the morgue. Elementary.