[Squawk 8888]

Very good question. There is no excuse for hitting a building even if there are mechanical problems; the regs require flying 1,000 feet higher than the tallest obstacle within a mile. Which means that it is either terrorism or an inept/careless/negligent pilot. The latter is more likely but I wouldn't rule our the former just yet.

[RSmithOpt]

If the bozo pilot lost power, had mechanical problems, etc., he should have / could have ditched the plane in the river if flying from west to east unless lost in fog.

I smell an intentional act.