This sounds like it was controlled flight into the building. He probably got disoriented while trying to fly up the river in marginal visibility and ended up with the building in his way with no time to react... especially as a new pilot.
See post #14. An experienced pilot, who owns a Cirrus SR20, describes how the plane reacts to a deep stall ... dips a wing, and goes into a spin. Combine this with confused descriptions of "aerobatic loops" and dropping a wing reported by witnesses. The two do sound rather similar, one from a pilot's perspective, and a layman's description from the ground.