"Would not many small attacks terrorize people? "
So far two are dead. They could buy an AK 47 and couple banana clips and kill 10 times that easily and not even get caught or die.
This is most likely and accident.
It's very tempting to try and shade the facts to fit a terrorist plot - but really - if someone's got a small aircraft in New York on October 11, 2006, the target is a packed, 50,000 seat Shea Stadium about the time the home plate ump yells "Play Ball!", not a half-empty upper east side apartment.
I hope you're right that this is an accident. But, remember, the whole idea of terrorism is not just to kill but to TERRORIZE. I have many friends who live in Manhattan high-rises and I'm sure they will not sleep well tonight or in the weeks to come.