Not convincing: it's lots easier to go around a building than to go over it -- especially if it's engine trouble.
Yes, it could be an accident. However, considering how this one building sticks up like a sore thumb over the city, it's difficult to believe that a pilot who's enough in control to talk on the radio, could just happen to run into such a small target.
I find it very hard to believe that's its an accident. A skilled pilot will do anything, anything, to avoid crashing into a crowded area. Even with engine trouble, there are lots of ways to affect a plane's flight angle.