Not at all. It's a great move. What if they didn't halt the busses and there were more incidences such as this? Then everyone would be complaining that they DIDN'T suspend the service. It's better to be safe than sorry.
Also remember that the plane that first crashed into the WTC building wasn't an isolated incident. How many more tragedies did the FAA prevent by immediately grounding all air flights?
Well, keep in mind that they haven't done that before. There have been other such incidents and Greyhound hasn't shut down their system. So, that's an indication of what I was *implying* in my statement above. It's that they know *something more* than we are being told (in the initial statements from them).
In other words, rather than me saying that is really an "over-reaction" -- it's in indication that this is a clue that there is more there than we are being told.
So, if there is nothing more than a whacko attacking a driver or hijacking a bus -- well, Greyhound has had that before and it's not been a problem for all the other busses running in their system. Thus -- an indication of "more".